Read the following context and choose the best option to answer the question.
Context: When I came back up , I heard enthusiastic WEE - OO - WEE - OO coming from his room . I popped my head in there and he made the noise at me and grinned . I asked " Firetruck ? "
Question: Why might he make that sound ?
Options: 
A. I said " firetrucks " so he made the noise .
B. He was playing make - believe with himself .
C. I like firetrucks so he made the noise .
D. He felt enthusiastic that I was in his room .


B