This question has two parts. First, answer part A. Then, answer part B.

Part A:

Which of these inferences about school classrooms is supported by the "Year–Round Schooling Helps Students, Teachers, and Families"?
A.
Year–round schooling makes scheduling classroom time easier.

B.
Year–round schooling can help schools utilize their existing classrooms better.

C.
Multi–track schedules allow teachers to teach students at different levels in the same classroom.

D.
Multi–track schedules make it easier for school districts to maintain and clean their classroom facilities.

Part B:

Which sentence from the "Year–Round Schooling Helps Students, Teachers, and Families" best supports your answer in part A?
A.
In addition, students can advance when they are ready rather than waiting for a new school year to start.

B.
Because some students are always on vacation, classroom populations are reduced.

C.
Teachers can provide more attention to the students on their track.

D.
Multi–track schedules also allow schools to register more students because their buildings are always in use.

Part A: The inference about school classrooms supported by the article is that Year–round schooling can help schools utilize their existing classrooms better.

Part B: The sentence that best supports the answer in Part A is "Because some students are always on vacation, classroom populations are reduced." This sentence suggests that having year-round schooling allows for more efficient use of classrooms as there are always some students on vacation, meaning that not all classrooms are occupied at once.

Part A:

B.
Year-round schooling can help schools utilize their existing classrooms better.

Part B:

C.
Teachers can provide more attention to the students on their track.

Part A:

The inference about school classrooms supported by the "Year–Round Schooling Helps Students, Teachers, and Families" is:

B. Year–round schooling can help schools utilize their existing classrooms better.

Part B:

The sentence from the "Year–Round Schooling Helps Students, Teachers, and Families" that best supports the answer in part A is:

B. Because some students are always on vacation, classroom populations are reduced.

To answer Part A, we need to analyze the options and find which inference about school classrooms is supported by the article "Year–Round Schooling Helps Students, Teachers, and Families."

A. "Year–round schooling makes scheduling classroom time easier."
This option suggests that year-round schooling improves the scheduling of classroom time. However, this inference is not directly supported by the given article.

B. "Year–round schooling can help schools utilize their existing classrooms better."
This option suggests that year-round schooling allows schools to make better use of their classrooms. As the article discusses the benefits of year-round schooling, it indirectly supports this inference by highlighting the advantages of utilizing classrooms throughout the entire year.

C. "Multi–track schedules allow teachers to teach students at different levels in the same classroom."
This option suggests that multi-track schedules allow teachers to teach students at different levels in one classroom. While the article mentions the benefits of multi-track schedules, it does not directly support this particular inference.

D. "Multi–track schedules make it easier for school districts to maintain and clean their classroom facilities."
This option suggests that multi-track schedules make it easier for school districts to maintain and clean their classroom facilities. Although the article mentions the benefits of multi-track schedules, it does not specifically support this inference.

Based on the analysis, the best inference supported by the article for Part A is option B: "Year–round schooling can help schools utilize their existing classrooms better."

Now, to answer Part B, we need to find the sentence from the article that best supports our answer for Part A.

A. "In addition, students can advance when they are ready rather than waiting for a new school year to start."
This sentence discusses the advantages of year-round schooling for students to advance when they are ready, but it does not directly support the inference about better utilization of classrooms.

B. "Because some students are always on vacation, classroom populations are reduced."
This sentence discusses the reduced classroom populations due to students being on vacation, but it does not directly support the inference about better utilization of classrooms.

C. "Teachers can provide more attention to the students on their track."
This sentence discusses how teachers can provide more attention to students on their specific track, but it does not directly support the inference about better utilization of classrooms.

D. "Multi–track schedules also allow schools to register more students because their buildings are always in use."
This sentence directly supports the inference for part A, as it mentions how multi-track schedules allow schools to utilize their buildings effectively by always having them in use.

Therefore, the sentence that best supports the answer for Part A is option D: "Multi–track schedules also allow schools to register more students because their buildings are always in use."