Ais usually a more accurate tool for estimating the number of calories you burn during a workout than internal calorie estimators on cardio machines.
a. step monitorb. body fat monitorc. bathroom scaled. heart rate monitor

Answer is D, Heart rate monitor.

Explanation:

It is known to be true that during exercise, the rate of the heart beat increases, and this is good for our heart to keep on functioning properly.

A heart rate monitor is usually a chest strap device to measure and sometimes record the rate of the heart's activities such as rate and rhythm. This device is with electrode sensors for transmitting heart rate to an app. Example of a heart rate monitor is Holter monitor.

complete the square on the right side of the equation;

-5(x + 0)^2 + 15

answer: d. y = -x^2 + 15