Why was Landon "grinning like someone who'd just won the lottery" at the beginning of paragraph two?

Responses
A He'd just gotten a report card full of high grades.He'd just gotten a report card full of high grades.
B He knew that his father had brought him a surprise gift.He knew that his father had brought him a surprise gift.
C He had a new pet that he was anxious to show off to his father.He had a new pet that he was anxious to show off to his father.
D He was happy to see his Dad and excited about their camping trip.

D He was happy to see his Dad and excited about their camping trip.