Question on Optical Isomerism

Out of (i) 2-methyl butanioc acid and (ii) 3-methyl butanoic acid, which one is optically active?

Answer:

One simple way to find out if an organic molecule is optically active or not is to check for the chiral carbon (a carbon whose valancies are satisfied by 4 different groups).

2-methylbutanoic acid has a chiral carbon and is optically active.