向日葵的子粒常有空瘪的主要原因是
A．施肥不足
B．传粉不足
C．灌溉不足
D．开的花少
答案：B
因为传粉不足，所以结出的子粒常常有缺粒的现象。
People are strongly advised _____ legal means to settle their disputes. [ ]
A. to take
B. taking
C. take
D. to be taken
架空乘人装置钢丝绳必须至少（）检查1次。
A、每天
B、每周
C、每月
