Stiffness in the neck can make it difficult for drivers to

The correct answer will be-problems to look backward is the correct answer.

Explanation:'

Stiffness is the state of a muscle which occurs due to the overuse of muscles which causes strain and pain in the muscles.

The stiffness can occur in any muscle but while driving we overuse the head and neck to drive safely during o which the neck muscles become stiff. This stiffness of neck muscles can cause certain problems while driving like it can cause the problem to look behind.

Thus, stiffness, while driving can cause problems to look backwards, is the correct answer.  

the correct answer is:

a population changes in response to a change in the environment.