Taking bus in Beijing______much cheaper than taking a taxi A is B be C are D were 说一下为什么
问题描述：
Taking bus in Beijing______much cheaper than taking a taxi A is B be C are D were 说一下为什么
答
Taking bus in Beijing__A___much cheaper than taking a taxi
A is B be C are D were
因为开始的Taking不是过去式,所以D去掉,句中a taxi 是单数,C去掉,be是完全没可能的,A是非谓语动词作主语,符合要求.