Answer:
Option 2 - 
Step-by-step explanation:
To find : Determine which polynomial is a perfect square trinomial?
Solution :
The perfect square trinomials are of the form :

Now, We check one by one which form make this satisfied.
1) 
We can re-write as
In this A=7x and B=4
Putting in formula,

So, The above equation will not form a trinomial.
2) 
We can re-write as
In this A=3a and B=5
Putting in formula,

So, The above equation will satisfy the form it is a trinomial.
3) 
We can re-write it trinomial form due to negative sign.
So, The above equation will not form a trinomial.
4) 
We can re-write it trinomial form due to negative sign.
So, The above equation will not form a trinomial.
Therefore, Option 2 is the only which make a perfect square trinomial.