Ping Pong is popular among China, _____ both young and old can _____. [ ]

A. about it; take part in

B. in it; take part

C. in which; take part in

D. in which; take part

DNA重组的步骤包括

A．将重组DNA导入受体细胞

B．将外源DNA与载体连接

C．培养细胞以扩增重组DNA

D．选出含有重组体的克隆