Choose the correct sentence (A, B, C or D) that has the same meaning to the given one.
It is too difficult for them to solve the problem by themselves.
A.Because the problem is very difficult, they can't solve it by themselves.
B.Unless the problem is difficult, they can't solve it by themselves.
C.They have no difficulty in solving the problem by themselves.
D.It is quite easy for them to solve the problem by themselves.