I couldn't help ____. A.to cry B.crying

选B

help to 是帮助的意思
help (to) do sth实际上有时候to是省略掉的。
help do sth

还有can't help doing sth.(忍不住/情不自禁去做某事）

help doing 是与can't一起用的

没有help doing 这种用法

hi:

answer is B

the reason is that the phrase of "could not help doing something" means you can not hold your feeling or emtotion in doing something..

i give you one more example

i could not help answering your question simply because it is easy for me anyway!!

hehe

tks

B.crying，can not help doing something是情不自禁的做某事

当然选B，意思是我情不自禁地哭起来。