Answer: The correct options are :
(4). (A)

(5). (C)

(6). (D)

(7). (C)

Step-by-step explanation: We are given to completely factor the following expressions :
Expression 4 :
The given expression is

The factorization of expression (i) is as follows :

So, option (A) is CORRECT.
Expression 5 :
The given expression is

The factorization of expression (ii) is as follows :

So, option (C) is CORRECT.
Expression 6 :
The given expression is

The factorization of expression (iii) is as follows :

So, option (D) is CORRECT.
Expression 7 :
The given expression is

The factorization of expression (iv) is as follows :

So, option (C) is CORRECT.