[单选题]Directions: In this part there is a sentence with one word or phrase underlined. Choose the one from the four choices marked A, B, C and D that best keeps the meaning of the sentence.The coach explained the regulations at length to make sure that none of his players would become violators.（ ）
A
at last
B
at once
C
in detail
D
in short
正确答案：C
本题考查常见介词短语的含义辨析。
at last“最终”， at once“马上”， in detail”详细地”， in short“简言之”。这里需要选择和at length“充分地，详尽地”相近的词，故选C。
