－The door was open.
－It ______ open. I had locked it myself and the key was in my pocket.
| A．can not be | B．must not be | C．can not have been | D．must not have been |
----What do you know the _____ of are the pig influenza in humans?
---- usually similar to regular human seasonal influenza .
| A．symptoms | B．sympathy | C．symbol | D．symptom |
People go out with masks,________.
| A．fear of swine flu. | B．afraid of swine flu. |
| C．fearing of the pig flu. | D．being afraid of swine flu.. |
The dead rate is _____ pigs and recovery usually ______ within 7-10 days.
A low in; occurs B.rich in;happens
C.high in; came aboutD.poor in;took place
_____ three influenza type A virus subtypes(子类型) have been found in pigs.
| A．By far | B．As far as | C．So far | D．Till far |
_____, experts point out that students can easily fail at starting their business because of a lack of preparations.
| A．But | B．However | C．while | D．though |