There are so many kinds of pens in the shop ,I can’t decide ______.

A．when to buy

B．where to buy

C．what to buy

D．which to buy

（）主要用来夹紧钢丝绳末端或将两根钢丝绳固定在一起。

A.卡环

B.绳夹

C.吊钩

D.吊环