现在要使一株结酸味的苹果树结出甜味苹果，下列哪项做法是错误的（　　）

A．将酸味苹果作为砧木

B．将甜味苹果作为接穗

C．将酸味苹果作为接穗

D．接穗与砧木的形成层要结合起来

— How long is it _____ you picked up your badminton training?

— It was not until my finance became better in last December _____ I started the training.

A．since; that

B．before; when

C．until; that

D．that; when