题目：
When _____ about one of the biggest concerns today, many citizens mentioned the sharp rise in housing price.
A．asking
B．to ask
C．asked
D．having asked
答案：
C
题目分析：考查非谓语动词。句意：当被问到当今关心的热门话题时，许多的市民提到房价的快速上涨。首先注意两个句子共用一个主语many citizens，市民与ask之间是动宾关系，故选C项。
考点 : 考查非谓语动词
