Answer:
Option D is correct.
Value of x is, 10 units.
Step-by-step explanation:
Triangle Proportionality theorem states that if a line parallel to one side of a triangle intersects the other two sides of a triangle, then the line divide these two sides proportionality.
Given that: 
From the given figure, we have;
AP = 3 units , PB = 6 units , QC = 20 units and AQ = x units.
then, by triangle proportionality theorem;

Substitute the given values, to find the value of x;

By cross multiply we have;

Divide both sides by 6 we get;
10 = x
Therefore, the value of x is, 10 units