[填空题]

The atmosphere is a mixture of several gases. There are about ten chemical elements which remain permanently in gaseous form in the atmosphere Under all natural conditions. Of these permanent gases, oxygen makes up about 21 per cent and nitrogen about 78 per cent. 41) _____________________________________________.The amount of water vapor, and its variations in amount and distribution is of extraordinary importance in weather changes. Atmospheric gases hold in suspension great quantities of dust, pollen, smoke, and other impurities which are always present in considerable, but variable amounts.
The atmosphere has no definite upper limits but gradually thins until it becomes imperceptible(难以察觉的). Until recently it was assumed that the air above the first few miles gradually grew thinner and colder at a constant rate. 42)_____________________________________________. Recent studies of the upper atmosphere, currently being conducted by earth satellites and missile probing(探查

[填空题]

The atmosphere is a mixture of several gases. There are about ten chemical elements which remain permanently in gaseous form in the atmosphere Under all natural conditions. Of these permanent gases, oxygen makes up about 21 per cent and nitrogen about 78 per cent. 41) _____________________________________________.The amount of water vapor, and its variations in amount and distribution is of extraordinary importance in weather changes. Atmospheric gases hold in suspension great quantities of dust, pollen, smoke, and other impurities which are always present in considerable, but variable amounts.
The atmosphere has no definite upper limits but gradually thins until it becomes imperceptible(难以察觉的). Until recently it was assumed that the air above the first few miles gradually grew thinner and colder at a constant rate. 42)_____________________________________________. Recent studies of the upper atmosphere, currently being conducted by earth satellites and missile probing(探查

[单项选择]The atmosphere is a mixture of several gases.
There are about ten chemical elements which
remain permanently in gaseous form in the atmo-
Line sphere under all natural conditions. Of these per-
(5) manent gases, oxygen makes up about 21 percent
and nitrogen about 78 percent. Several other
gases, such as argon, carbon dioxide, hydrogen,
neon, krypton, and xenon, comprise the remaining
1 percent of the volume of dry air. The amount
(10) of water vapor, and its variations in amount and
distribution, are of extraordinary importance in
weather changes. Atmospheric gases hold in sus-
pension great quantities of dust, pollen, smoke,
and other impurities which are always present in
(15) considerable, but variable amounts.
The atmosphere has no definite upper limits
but gradually thins until it becomes imperceptible.
Until r
A. New Methods for Calculating the Composition of the Atmosphere
B. New Evidence Concerning the Stratification of the Atmosphere
C. The Atmosphere: Its Nature and Importance to Our Weather
D. The Underlying Causes of Atmospheric Turbulence
E. (E) Stratosphere, Troposphere, Ionosphere: Three Similar Zones

[简答题]PassageB By2050,forthefirsttimeinhistory,therewillbemorepeopleintheworldoverage65thanunderage14.TheGlobalCityIndicatorsFacility(GCIF)inTorontohaspartneredwithPhilipsintheNetherlandstoreleaseanewreportonCitiesandAging.Thispolicysnapshotoutlinesstrategiesforaddressingtheneedsofouragingurbanpopulation,andshowshowinternationallystandardizedindicatorsof“age‐friendlycities”canbeusedtobenchmarkandpredictscenariosforbetter‐informeddecision‐making.Thereport,andGCIF’songoingresearch,willinformandguidecityleadersonhowtobetterconfrontthechallengesassociatedwithanagingpopulation. Globally,peopleovertheageof65willincreaseby183percentby2050.InpartsofAfrica,theincreaseisastartling366percent.Atthesametime,urbanizationhasbecomeadefiningphenomenonofthe21stcentury,anditisprojectedthat70percentoftheworld’spopulationwillliveincities.Giventhesetwocriticalpopulationshifts,thisrapidlyagingworldsignifiesrapidlyagingcities. Municipalpolicydecisionsarebecomingincreasinglyvitaltothestateofthewor
A. A．we should take the accessibility of care facilities and health services into consideration.
B．the government has to prolong the working time of the old who are expected to retire later.
C．the young have many more old people to take care of and their happiness index will decrease.
D．the developing speed of our economy will slow down for the lack of efficient labors.