179. Please don’t _____ a joke on the disable. We should try our best to help them.
She can’t help ______ for her family often, so she can’t help ______ why life is so hard.
He started to learn English in 1990 and in the years ________ he kept on using it in his work.
Excuse me for breaking in, ______ I have some news for you.
Why pleasant smells do not reduce pain in man is a question still _______ by scientists.
I am told to guess the meaning of an unknown word, but my question is _______ I still can’t understand its meaning.