To save time， many students have _________ lunch at school every day．（　　）

A．aB．anC．/D．the

Oh． my God! I forgot to bring my pen here．

Don't worry． I have two． You can use __________．（　　）

A．IB．meC．myselfD．mine

Betty has a beautiful _________． She wants to be a singer in the future．（　　）

A．voiceB．lookC．noiseD．sound

What do you think of working as a doctor？

It 's a good job to help people keep___________．（　　）

A．busyB．strictC．healthyD．generous

Will you stay here for dinner with us？

Sorry， I ____________． My mother is waiting for me at home．（　　）

A．mustn'tB．can'tC．needn'tD．couldn't