. At the meeting they discussed three different ____to the study of mathematics
—Are there any English story books for us students in the library? —There are only a few, ______.
I have experienced quite a number of cases ______ I really wanted to help but could not have anything to ______.
_______ of taking a bribe(贿赂), the official was being investigated.
—What about the student in your class, Mr. Wang?—The doctor said that ________ sleep caused him poor memory and poor concentration.
____________ many times, but he still couldn’t understand it.