$CH_3-CH_2-CH_2-COOH$ and $CH_3-CH(CH_3)-COOH$ are examples of:

Tautomerism is exhibited by

Which of the following methods of structural formula representation conventionally uses a point for the front carbon and a circle around it for the rear carbon?

Which of the following is not a pair of functional isomers?

Which of the following substances is not an isomer of $3$-ethyl-$2$-methylpentane?

Write the types of isomers for $C_4H_6$ (alkyne) and provide one example for each.