题目

已知某RNA一端的三个碱基顺序是GAU，它所转运的是亮氨酸，那么决定此氨基酸的密码子是由下列哪个碱基序列转录而来 A．GAT     B．GAU     C．CUA        D．CTA 答案：----What were you doing this time yesterday?----I ________ my homework at John’s house.A．doB．am doingC．didD．was doing