High blood pressure in mammals reflexively causes a decrease in heart rate, which results in lowered blood pressure. This is a feedback loop because response to the signal results in a(n) of that signal.

That's a negative feedback loop because response to the signal results in a decrease of that signal.

Explanation:

Decreased blood pressure decreases baroreflex activation and causes heart rate to increase and to restore blood pressure levels

The correct answer is 4. Being startled is a reflexive action, and waving to a friend is a voluntary action.

Reflexive action occurs involuntarily in a response to a stimulus whereas, a voluntary action is consciously done by a person. The person has total control on the action. A voluntary action is controlled by the brain and involuntary action is controlled by the spinal cord.

Therefore, in the given question, being startled is a reflexive action, and waving to a friend is a voluntary action.