问题
选择题
In order to reduce the increasing prices of vegetables，the toll(过路费) if a truck carrying them passes through a toll sration.
A．cancels
B．is canceiled
C．was cancelled
D．had been cancelled
答案
答案：B
考查动词时态和语态。cancel与thetoll之间是被动关系，而且是目前状况，所以用一般现在时的被动语态。
。在催化剂存在下，由苯和下列各组物质合成乙苯最好选用的是