Which of the following biphenyls is optically active?

Indicate whether each of the following pairs are identical, or ?

$I$  ||  $II$  ||  $III$

Total number of compounds with Chiral carbon atoms from following is___________.   $IMAGE$

$ \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}\left(\mathrm{NO}_2\right)-\mathrm{COOH} $

$ \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CHBr}-\mathrm{CH}_2-\mathrm{CH}_3 $

$ \mathrm{CH}_3-\mathrm{CH}(\mathrm{I})-\mathrm{CH}_2-\mathrm{NO}_2 $

$ \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}(\mathrm{OH})-\mathrm{CH}_2 \mathrm{OH} $

$ \mathrm{CH}_3-\mathrm{CH}-\mathrm{CH}(\mathrm{I})-\mathrm{C}_2 \mathrm{H}_5 $

Which of the following exhibits optical isomerism

Which is optically active

Incorrect statement