Question

Acetone and Propanal are:
A .functional isomers
B. position isomers
C .geometrical isomers
D .optical isomers

Answer 1

Hint: Molecular formula for Acetone is $C_3{H}_{6}O$ and molecular formula for propanal is $C_3{H}_{6}O$ which means they have the same molecular formula. But one is from the ketone family whereas another from the aldehyde family.

Complete step by step answer:
Firstly what is the definition of an isomer?
The term isomer means each of two or more compounds with the same formula but a different arrangement of atoms in the molecule and different properties.
Isomers can be split into two broad groups – structural (or constitutional) isomers and stereoisomers and structural isomer classified into three groups, chain isomer , position isomer and functional isomer
Now let us see all options with detailed information
A.functional isomers
Occurs when the same molecular formula but differs in the functional group.
Examples:
A.Acetone

-Propanal( Propanaldehyde)

So from this we can conclude Acetone and Propanal are functional isomers hence option A is the correct answer.
B.Position isomers:
Occurs when the functional group is in a different position on the same carbon chain.
Example:
$1-$ chloropropane
$2-$ chloropropane
C.Geometrical isomers:
Two or more compounds differ from each other in the arrangement but same in the structure
Example:
cis - but $-2-$ ene
trans - but $-2-$ ene
D.Optical isomers:
Optical isomers are compounds that are non-superimposable mirror images of each other. ... If the arrangement in space makes the two isomers non-superimposable mirror images of each other, we call them optical isomers or enantiomers. An example is the amino acid alanine.
So, the correct answer to this is option A.

Note: In geometrical isomerism the arrangement is differ from double bond or ring and non-superimposable mirror images forms. Non- superimposable mirror images are the ones in which we can distinguish the left and right side of the object. Examples like “MOM” are the same in its mirror image too.