读对话，判断正(T)误(F)。

A: Do you have new teachers, Tom?

B: Yes.

A: Who are they?

B: Mr. Lin and Mr. Sun.

A: Are they young?

B: Mr. Lin is young, but Mr. Sun isn't.

A: Is Mr. Lin a university student?

B: Yes, he's very funny.

A: Is Mr. Sun strict?

B: Yes, and we all like them very much.

( ) 1. Tom has two new teachers.

( ) 2. Mr. Sun isn't strict.

( ) 3. Mr. Lin is young. Mr. Sun is old.

( ) 4. Mr. Lin is funny.

( ) 5. Tom likes his new teachers very much.

触发电路主要是用（）。

A、二极管

B、三极管

C、场效应管

D、单结晶体管