Identify correct statements from the following : A. Propanal and...

A. Propanal ($CH_3CH_2CHO$) and propanone ($CH_3COCH_3$): Same formula $C_3H_6O$, different functional groups (aldehyde vs ketone) → Functional isomers. True
B. Ethoxyethane ($C_2H_5OC_2H_5$) and methoxypropane ($CH_3OC_3H_7$): Same ether group, different alkyl groups → Metamers. True
C. But-2-ene ($CH_3CH=CHCH_3$): No chiral carbon, shows geometrical isomerism (cis-trans), not optical. False
D. But-1-ene and but-2-ene: Both are alkenes, differ in position of double bond → Position isomers, not functional isomers. False
E. Pentane and 2,2-dimethylpropane: Both $C_5H_{12}$, different carbon skeleton → Chain isomers. True
Correct: A, B and E only.