Dalton wondered why the heavier and lighter gases in the atmosphere did not separate as oil and water do.He finally concluded that the constituent__1__must exist in the form of __2__ particles or atoms and that these __3__ be completely mixed together in the__4__.This threw a new light in__5__laws of definite proportions.It was__6__necessary to suppose that the atoms__7__combinesintossmall groups of uniform__8__and so form more complex substance; __9__ the mystery of this law was__10__.Dalton suggested, for example, that carbon monoxide__11__formed by the one with one__12__of atoms of carbon and oxygen, __13__ carbon dioxide results from a single__14__of carbon uniting with two atoms__15__oxygen.Assuming this to be true,__16__the definite proportions of Prout's law ( __17__ all chemical compounds the different constituents__18__enter in unvarying proportions) would naturally__19__the relative weights of the many__20__kinds of atoms.
1.A.gases B.pieces C.things D.gas
2.A.timely B.trimmed C.tiny D.topical
3.A.ought B.could C.will D.must
4.A.sky B.atmosphere C.oxygen D.environment
5.A.various B.many C.the D.those
6.A.only B.too C.that D.extremely
7.A.should B.were C.get D.could
8.A.construct B.structure C.piece D.feature
9.A.but B.also C.thus D.nevertheless
10.A.solved B.discovered C.broked D.told
11.A.must B.been C.were D.is
12.A.putting B.pairing C.placing D.preparing
13.A.while B.when C.therefore D.also
14.A.piece B.type C.atom D.measure
15.A.from B.in C.of D.for
16.A.then B.so C.by D.that
17.A.from B.in C.to D.for
18.A.are B.wouldn?t C.always D.never
19.A.describe B.unit C.mix D.reveal
20.A.different B.usual C.important D.chemical