What’s wrong with him? I haven’t seen him _____ last Wednesday.A. on B. since C. by
—What are you reading about?—It’s about the one-child policy. It says that the policy has_____ controlling the population in China.
Maria has _____ trouble _____ math, so she often asks her math teacher for help.
The rivers in Changshun are clearer than _____ in Wuhan..
—Does your father still smoke?—No, he has succeeded in_____ smoking for three years.
I think that you have made rapid _____ in math.