Which of the following statements about reinforcement is true?
a) reinforcement is a type of natural selection.
b) reinforcement increases the number of intermediate phenotypes.
c) reinforcement is also called dispersive selection.
d) reinforcement decreases the morphological difference between two incipient species.

The correct answer is option a, that is, it is a kind of natural selection.

Explanation:

A procedure of speciation in which the phenomenon of natural selection enhances the reproductive isolation amongst the population of two species is known as reinforcement. This takes place as a consequence of selection functioning against the generation of hybrid entities of low fitness.  

The concept was developed originally by Alfred Wallace, also considered as the Wallace effect. Reinforcement signifies towards some of the circumstances in which selection can encourage an enhancement in prezygotic isolation, affecting the procedure of speciation straightforwardly.  

1. Species diversity.

2. stem that stores water.

3. invasive species.

4. migrating farther into the sea.

5. genetic diversity.