Many married women manage to go out to work and ______ a home as well.

A.universal

B.compulsory

C.requested

D.general

_ on roofs and telegraph wires.These birds are swallows.They are __62__ together because, very soon, they will be flying __63__ to much warmer lands, where they will find __64__ the small flying insects on which they __65__.There are no such insects __66__ in Britain during the winter; it is __67__ cold for them.

The swallows settle, fly off, swoop, and __68__ again.this they do many times, for they are making short __69__ flights in order to be fit for the long journey __70__ them.

__71__ of these migrating birds leave Britain in the autumn.They fly __72__ for hundreds of miles __73__ they reach the warm lands of Africa.But not all the birds get there, for many of them perish in the stormy weather they meet with __74__.

In the spring of the following year they __75__ the long and tiring journey back to Britain.They return to the identical barn or tree in the __76__ district which they had left the __77__ autumn.How do these birds find their__78__ there and back over such vast distances？ Nobody knows exactly __79__, but it has something to do __80__ winds and air currents.

61.a.being perched b.perched c.being perching d.be perched

62.a.gathering b.assembling c.waiting d.forming

63.a.to south b.the south c.to southwards d.south

64.a.a great number of b.a great deal of c.plenty of d.numerous

65.a.feed b.are fed c.eat d.rely

66.a.near b.about c.nearby d.over

67.a.too b.a bit c.very d.much

68.a.fly off b.swoop c.settle d.turn back

69.a.practical b.practicing c.practice d.practiced

70.a.in advance b.ahead of c.in front of d.in front

71.a.Swarms b.Herds c.Flocks d.Schools

72.a.firmly b.stoutly c.harshly d.steadily

73.a.until b.before c.when d.as

74.a.in the way b.on the way c.half the way d.all the way

75.a.take b.fly c.find d.make

76.a.old b.original c.familiar d.identical

77.a.before b.previous c.above going d.former

78.a.way b.path c.course d.route

79.a.why b.when c.how d.what

80.a.against b.away c.for d.with

设MN，证明：M∩N=M，M∪N=N。

A.5μm～10μm

B.10μm～50μm

C.50μm~75μm

D.75μm～100μm

E.>100μm

大红细胞直径为

A．＜6μm

B．＞9μm

C．＞10μm

D．＞15μm

E．＞20μm

飘尘的粒径在

A．100/μm以下

B．10μm以下

C．5μm以下

D．2.5μm以下

E．0.4μm以下

PM2.5是指直径

A．＜2.5μm的颗粒物

B．2.5μm＜颗粒物＜10μm

C．2.5μm＜颗粒物＜5μm

D．=2.5μm的颗粒物

E．≤2.5μm的颗粒物

A.<20μm

B.<15μm

C.<10μm

D.<5μm

E.<3μm

A、≤0.1μm

B、≤10μm

C、≤5μm

D、≤1μm

E、≤100μm

可吸入性纤维粉尘是指

A．直径＞3μm，长度＜5μm

B．直径＞3μm，长度≥5μm

C．直径＜3μm，长度＜5μm

D．直径＜3μm，长度≥5μm

E．直径3＜μm，长度≥9μm