Answer:- 
Explanations:- Let's say the first molecule is A and the second molecule is B and the product molecule is C.
From given information, 2 molecules of A react with 3 molecules of B to produce 5 molecules of C.
We write the reactants on left side and the product on right side and there is an arrow between them from reactants towards the products.
So, the reaction could be represented as:

Polyethylene terephthalate commonly abbreviated as PET
Answer:
A. It keeps the electrolyte solutions neutral.
Explanation:
The electrons flow from the anode to the cathode and the problem is that the cathode may become too negative. The purpose of the salt bridge is to maintain charge balance because the electrons are moving from one-half cell to the other.
The answer is D
FeCl3 + 3 NH4OH → Fe(OH)3 + 3 NH4Cl