11) The subject of these lectures ____by the lecture committee.A) is announced B) have been announcedC) are announced D) has been announced12) I found an aspirin bottle ____dropped on the floor of David's room.A) was B) had C) had been D) is13)The go

11) The subject of these lectures ____by the lecture committee.A) is announced B) have been announcedC) are announced D) has been announced12) I found an aspirin bottle ____dropped on the floor of David's room.A) was B) had C) had been D) is13)The go
11) The subject of these lectures ____by the lecture committee.
A) is announced
B) have been announced
C) are announced
D) has been announced
12) I found an aspirin bottle ____dropped on the floor of David's room.
A) was B) had C) had been D) is
13)The goods ____when we arrived at the airport.
A) were just unloading
B) were just been unloading
C) had just unloaded
D) were just being unloaded
14) If one ____by pride,he will reject useful advice and friendly assistance.
A) overcomes B) is overcomeC) has been overcome D) overcome
15) Most environment problems exist because adequate measures for preventing them ____taken in the past.
A) was not B) were not C) were not being D) had not been
16) You ought to have put the milk in the refrigerator,now ____sour.
A) I smell B) it is smeltC) it smells D) it is smelling
17) After the race____,the celebration began.
A) had been won B) is wonC) will be won D)has been won
18) He was here for a little while,but I don't knowswhereshe ____now.
A) is B) was C) had been D) has been
18) The young teacher has ____ competent.
A) been proved to be B) proved to beC) been proved D) proved being
19) Pluto,the outermost planet of the solar system,____photographically in March 1930.
A) discovered B) was discoveredC) by discovery D) when discovered
20) To get a better view of the stage,____.
A)our seats had to be changed
B) our seats were changed
C) we had to change our seats
D) our seats were changed by us

11) The subject of these lectures ____by the lecture committee.A) is announced B) have been announcedC) are announced D) has been announced12) I found an aspirin bottle ____dropped on the floor of David's room.A) was B) had C) had been D) is13)The go
11.A) is announced； 主语subject ...是单数
12.C) had been；I found 用的过去式,bottle 被 drop 肯定发生在更早,过去完成时
13.D) were just being unloaded；恰恰正在被卸下
14.B) is overcome；被动语态假设语气 overcome 的过去分词仍是overcome
15.B) were not; adequate measures 复数,被动语态
16.C) it smells；尽管是现在,milk 本身无法采取进行式
17.A) had been won；随后the celebration began(过去式）
18.C) been proved；被证明+形容词
19.B) was discovered; Pluto was discovered ...有没有当中那些形容的字眼都一样.
20.C) we had to change our seats; 是 we get a better view,不是 our seats
希望对您的理解能有点帮助 ...