In ___ year 751, the Chinese traveler Du Huan was taken __ _ prisoner by the Arabic army.
Understanding the cultural habits of another nation, especially ____________ containing as many different subcultures as the United States, is very difficult.
As we all know, apples are sold by ____ weight, and socks are sold by _______dozen.
Many difficulties have ______ as a result of the changeover to a new type of fuel.
——Why are the tax collectors so busy? ——Many people prefer to have their tax forms completed by a professional rather than ___.
It was in the small house _______ was built with stone by his father _______ he spent his childhood.