问题
选择题
Collecting stamps as a hobby___________ increasingly popular during the past fifty years.
A．becomes
B．became
C．has become
D．had become
答案
C
主语collecting stamps as a hobby被看成是整体，谓语动词用第三人称单数形式。而时间状语during the part fifty years限制了句子用完成时态。
【标签】动名词作主语