D. Salt and water
Explanation:
Acid + Alkali -> Salt + water
<span>In the field of science, usually, the product of an experiment is
computed ahead to understand if it reached a specific objective. It would reach
greater than 100% of percent yield if the factors include faster reaction rates;
proper handling of the reactants, no outside contaminants, and the procedure of
the experiment is followed smoothly. It would reach lesser than 100% percent yield
if the experiment is not followed, external factors such as contamination from
the environment (wind, moisture, etc). </span>
The central atom is carbon with three hydrogen and one chlorine atom around it. There are no unshared electrons on the carbon so it is tetrahedral.
You start by diving each quantity given by the atomic wight of each element:
Phosphorus (P) 
Hydrogen (H) 
Then you divide by the lowest number:
for phosphorus
for hydrogen
So the empirical formula will be:
