下面两个式子结果相同的是 [ ]
A.a×2和a2
B.m+n和2m
C.a-b-c和a-（b+c）
答案：C
3克碳燃烧生成多少克二氧化碳？
The thieves _____ him _____ in the park, took his wallet and escaped.
A．held .. back
B．held .. up
C．held .. on
D．held .. out
