Answer:
B
Step-by-step explanation:
Allopatric speciation means the process happened because of a physical barrier while sympatric speciation means they diverged while being in the same region.
In this beetle example, divergence happens in the same geographical area. It is a sympatric speciation.
The mutant version of the plant becomes more common with the passage of time and one variant of beetle prefers it. Knowing that beetles not only pollinate the flowers but also mate inside them we can deduce there is an environmental barrier that over time makes them diverge. Individuals exploit different conditions from the same region.
Correct answer is B, sympatric speciation and the drive force is habitat differentiation.