It is difficult to understand this kind of ____ calculation.

A) difficulties in finding C) difficulty to find

B) difficulty in finding D) trouble to find

A) forward C) out

B) about D) to

A) cannot help to laugh C) cannot but laughing

B) cannot help laugh D) cannot help but laugh

A) many among C) many ones of which

B) many in which D) many of which

A) made C) having made

B) being made D) to be made

A) increasing B) increase C) to increaseD) have increased

A) except for B) besides C) except that D) because

A) come B) to come C) coming D) having come

A) must fall B) must have fallen C) should have fallen D) can have fallen

A) will graduate C) will have graduated

B) will be graduated D) will be graduating