Which type of isomerism is exhibited by acetic acid $(CH_3COOH)$ and methyl formate $(HCOOCH_3)$?

Which of the following is a pair of metamers?

Which of the following are meso compounds?

Tautomerism is exhibited by

Given below are two statements :
Statement $(I) :$ $CH_3CH=CHCH_3$ and $cyclobutane$ are isomeric compounds.
Statement $(II) :$ $CH_3CH_2CH_2CH_2NH_2$ and $(CH_3CH_2)_2NH$ are functional group isomers.
In the light of the above statements,choose the correct answer from the options given below :

The compound which shows metamerism is: