单项选择 -Where's Mike? -He is working ( ) physics ( ) in the classroom. A.in;problemB.out;problemC.in;problemsD.on;problems

问题描述:

单项选择 -Where's Mike? -He is working ( ) physics ( ) in the classroom. A.in;problem
B.out;problem
C.in;problems
D.on;problems

D.on;problems
work on从事,演算