Answer :
The isomers mean that these substances have the same constitution but with different structure. So among the four choices, the (2) CH3CH2CHO and CH3COCH3 is right.
Answer: Option (2) is the correct answer.
Explanation:
When two or more compounds have same chemical formula but different structural arrangements of their atoms then they are known as isomers.
For example, [tex]CH_{3}CH_{2}CHO[/tex] and [tex]CH_{3}COCH_{3}[/tex] both have same chemical formula as [tex]C_{3}H_{6}O[/tex].
The only difference between them is the arrangement of atoms.
Thus, we can conclude that the compounds CH3CH2CHO and CH3COCH3 are isomers of each other.