中国居民DRIs建议，幼儿每日膳食钙的适宜摄入量为（）
A.400mg
B.600mg
C.700mg
D.800mg
E.900mg
参考答案：B
__________ difficult the task may be, we will try our best to complete it in time.
A．Whatever
B．No wonder
C．Though
D．However
YJ29接装机负压表显示板上共有（）个负压表监控显示各部的负压状况。
A.3
B.5
C.6
D.4
