问题补充：
Listen! There’s a lot of noise from next door. They a party.
A. could have had
B. must be having
C. should have had
D. can be having
答案：
A. could have had
(答案→)B. must be having
C. should have had
D. can be having
解析：考察虚拟语气.句意:听!隔壁有很多噪音.他们一定是在举行一个聚会.must be表示对现在的情况的肯定地推断,故选B.
