It looks _______ it were going to rain.
— How did you find your visit to Lijiang River? — To tell the truth, it’s hard to _______ a more fascinating place.
I joined a club while at college, _______ members were all literary lovers.
He spoke English so well that I took _______ for granted that he was an American.
Taking medicine only gives you _______ relief from pain, so I suggest you have an operation.
It was nothing but his ten years of hard work that _______ his success in his research.