I am so tired，for I English for 2 hours.
A. is studying
B. have been studying
C. was studying
D. had been studying
网友回答
A. is studying
(答案→)B. have been studying
C. was studying
D. had been studying
解析：句意：我好累，因为我已经学习英语两个小时了。根据“for 2 hours”可知，此处表示动作从过去某一时间开始，一直延续到现在，可能还要继续下去，故应用现在完成进行时。