He helps his mother _______________ housework. [ ]
A. does
B. do
C. did
D. doing
答案:B
家里连接灶具的胶管最长不能超过多少米?()
A.1米
B.2米
C.3米
定量食物频率法与定性食物频率法的区别是,定量食物频率法关注()
A.是否摄人某种食物
B.摄入量有关细节
C.进食频率
D.摄入开始时间和持续时间长短