催化剂密相装填时，可以采用（）作为催化剂装填的推动力。
A、人力
B、压缩空气
C、压缩氮气
D、机械动力
参考答案：B, C, D
My parents ______ born in Shanghai, but I ______ born in Nanjing.[ ]
A. was, was
B. were, was
C. were, were
D. are, am
“又灌溉三郡，开稻田，于是蜀沃野千里，号为陆海，旱则引水浸润，雨则杜塞水门。”这是对哪一水利工程的评价（）
A.都江堰
B.郑国渠
C.坎儿井
D.白渠
