题目

下列化合物的组成中，含有胸腺嘧啶的是                                        （    ）    A．ATP            B．tRNA          C．mRNA           D．DNA 答案：DWhat a pity! I missed meeting my boss at the airport because my car was _____in the traffic jam.A. broken up       B. broken down      C. held up         D. kept up