Which of the following compounds is optically active?

Explain: Butan-$2$-ol is chiral (asymmetric) and optically active.

The optically active tartaric acid is named $D-(+)$ tartaric acid because it is related to $D-(+)$ glyceraldehyde in terms of:

$A$ disymmetric object is one which is:

$A$ compound contains $3$ chiral carbons. What is the number of possible optical isomers for this compound?

The specific rotation of $(+)$-Mandelic acid is $+158^o$. What will be the specific rotation of a mixture containing $25\%$ $(-)$-Mandelic acid and $75\%$ $(+)$-Mandelic acid?