题目

一条多肽链中有500个氨基酸，则合成该多肽链的mRNA分子和用来转录mRNA的DNA 分子至少有多少个碱基（    ） A．1500个和1500个                  B．500个和1000个 C．1000个和2000个                      D．1500个和3000个 答案：D Many people in the west make ________ a rule to buy Christmas presents for their relatives and friends. A．thisB．itC．thatD．them