he was a rising film star in China, but now few young people know him.
A. At a time
B. All the time
C. At one time
D. At times
网友回答
A. At a time
B. All the time
(答案→)C. At one time
D. At times
解析：
这题考查词组：At a time一次，.All the time一直，.At one time曾经，At times有时，
根据句意：他曾经是中国的崛起的电影明星，可是现在很少年轻人认识他，选C。