【单选题】Which of the following gases represents the greatest threat to personnel safety in an engine room where the exhaust is leaking from a diesel engine?
【单选题】_____________ trees are there in your village? [ ]
【简答题】在三极管放大电路的三种基本组态中,()带负载的能力最强。
【单选题】—______? —She is twenty.
A.
What’s your grandmother’s age
B.
How old is your brother
C.
How old is your sister
D.
When is your sister’s birthday