题目

You can't imagine ___________when they received these nice Christmas presents. A . how they were excited B . they were how excited C . how excited were they D . how excited they were 答案：D在双链DNA分子中，已知A≠C，下列各项正确的是: A．（A+T）/（G+C）＝1                                  B．（A+C）/（G+A）＝1 C．（G+C）/（A+T）＝1                                  D．（A+G）/（T+C）≠1