—Congratulations！I hear you’ve won the first prize in the singing competition．—You _____ be mistaken．I’m in the dance class．
| A．must | B．may | C．should | D．could |
How did it______ that humans speak so many different languages?
| A．come out | B．come off | C．come about | D．come round |
Eric was well prepared for the computer test so that he could be positive about passing it on his first________.
| A．intention | B．attempt | C．purpose | D．desire |
The dead rate is _____ pigs and recovery usually ______ within 7-10 days.
A low in; occurs B. rich in;happens
C. high in; came about D. 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 |