mRNA上的四种核苷酸能组成多少种密码子（）
A.4
B.16
C.61
D.64
E.81
参考答案：D
已知圆锥的母线长为30，侧面展开后所得扇形的圆心角为120°，则该圆锥的底面半径为______．
--- I don’t care what people think.
--- Well, you __________. People’s idea is of great value to you.
A．could
B．would
C．should
D．might
