800÷4÷2=800÷(4÷2)…______.
800÷4÷2
=800÷(4×2),
=800÷8,
=100;
800÷(4÷2),
=800÷2,
=400;
故答案为:错误.
-Do you mind my taking this seat?
-____ . It's for Mr. Smith.[ ]
A. Not at all
B. Yes, pleaseI
C. Yes. of course not
D. You'd better not
疟疾的传染源是()
A.病人
B.受感染的动物
C.带虫者
D.病人及带虫者
E.带毒者