单选题 It's a fine day. Let's go for a walk, ___?

单选题 —Must I do my homework at once? —No, you ___.

单选题 There ___ different classes in our school.

单选题 Tina wants to be a singer ___ she is good at singing.

单选题 ___ you didn't sleep last night, you may take a rest now.

单选题 I also need an English certificate ___ we do business with foreign companies.

单选题 ___ communication skills ___ computer skills are important.

单选题 ___ is necessary to get certificates.