Plants like the stinging nettle seen here have sharp, needle-like hairs that inject a burning chemical into animals that touch the stems or leaves. These hairs are used for A) protection. B) reproduction. C) photosynthesis. D) attracting insects.

A. Protection

Explanation:

These plants have this external protection system to protect them against being eaten by these animals.

In cases where these plants are approached to be eaten by these animals, these systems which in this case are these hairs tend to make an effort by discomforting the approaching animals.

The animals upon sensing this discomfort retreat from feasting on these plants which thus prolongs their lives and prevent them from being eaten by these animals