．______Hard you may try, you can’t possibly persuade Tom to give up smoking, for he is so addicted to it.

A．Whatever

B．However

C．Whichever

D．Whenever

盛装过石灰水的试剂瓶内壁常会形成一层白色的膜，除去它的方法是（　　）

A．加洗洁精清洗

B．用热水清洗

C．加稀盐酸清洗

D．加氢氧化钠清洗