脊柱前凸常见的原因有（）
A.脊椎骨软骨炎
B.大量腹水
C.脊椎结核
D.腹腔巨大肿瘤
E.晚期妊娠
参考答案：B, D, E
I’m sorry I can’t help ___________ the flowers, because I’m busy preparing for the singing competition _____________ tomorrow.
A．watering; to be held
B．water; being held
C．to water; held
D．to water; to be held
我国古典园林发展的转折期出现在（）时期。
A.秦、汉
B.魏、晋、南北朝
C.隋、唐
D.明、清
