which enzyme of the TCA cycle catalyzes a reaction very similar to that catalyzed by the pyruvate dehydrogenase complex

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

Can someone me with these questions plz.

Draw any one of the skeletal structures of a 2° alkyl bromide having the molecular formula of c6h13br and two stereogenic centers. indicate chirality by using wedge and hashed wedge notation. lone pairs do not need to be shown.