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

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.

sound moves fastest in solids because the molecules are tightly packed and it allows sound to vibrate