Which is an adequate description of the compounds shown in the diagram?
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H-C-C-C-C-OH
! ! ! !
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H-C-C-C-C-H
ĊĊ-
HH OHH
1.
They are isotopes of butanol.
2.
They are isomers of butanol.
3.
They are alkanes.
4.
They are alkenes.

the correct answer to it will be

2. They are isomers of butanol

as In the first case the the position of the alcoholic group is in the 1st carbon atom of butane and in the second its located at the 2nd carbon atom of butane.

so the compound is same with same chemical formula but since the postion of alcoholic group is different in both they become each other's isomers.