问题补充:
---Can you tell me how often he practices his English?
---.
A. At times
B. At one time
C. At all times
D. At a time
答案:
(答案→)A. At times
B. At one time
C. At all times
D. At a time
解析:考查介词短语:A. At times有时,B. At one time曾经,一度,C. At all times一直,D. At a time一次,句意:--你能告诉我他多长时间练一次英语吗?--有时。选A。