Combine these two simple sentences into a complex sentence.

Many industrialized nations use the metric system. The United States refuses to adopt it.

A. Although many industrialized nations use the metric system, the United
States refuses to adopt it.
B. Many industrialized nations use the metric system, but the United States
refuses to adopt it.
C. Many industrialized nations use the metric system; however, the United
States refuses to adopt it.
D. Many industrialized nations use the metric system, but the United States
refuses to adopt it.

Yes, A.

Wouldn't all of them technically be right?

Thanks for the help!

You're welcome.

D. Many industrialized nations use the metric system, but the United States refuses to adopt it.

To combine these two simple sentences into a complex sentence, you can use coordinating conjunctions like "although," "but," or "however." These conjunctions can help show a contrast or contradiction between the two ideas.

Here are the options:

A. Although many industrialized nations use the metric system, the United States refuses to adopt it.

This sentence uses the coordinating conjunction "although" to introduce the contrast between the metric system being used by many industrialized nations and the United States refusing to adopt it.

B. Many industrialized nations use the metric system, but the United States refuses to adopt it.

This sentence uses the coordinating conjunction "but" to indicate the contradiction between the metric system being used by many industrialized nations and the United States' refusal to adopt it. This conjunction is commonly used to express a difference or unexpected outcome.

C. Many industrialized nations use the metric system; however, the United States refuses to adopt it.

This sentence uses the conjunctive adverb "however" to show the contrast between the metric system being used by many industrialized nations and the United States' refusal to adopt it. This adverb acts as a transition between the two ideas.

D. Many industrialized nations use the metric system, but the United States refuses to adopt it.

This option is the same as option B, where the coordinating conjunction "but" is used to introduce the contrast between the metric system being used by many industrialized nations and the United States' refusal to adopt it.