Exocrine glands differ from endocrine glands in that exocrine glands:

Circadian rhythm is the term for the biological clock that regulates the sleep-wake cycle and other physiological processes in the body.
Melatonin is a hormone that is produced by the pineal gland in the brain in response to darkness.
It helps with the timing of the circadian rhythm and promotes sleep.
Choice A is wrong because metabolic rate is not affected by light exposure, and thyroxine is a hormone that regulates metabolism, not sleep.
Choice B is wrong because the limbic system is a part of the brain that is involved in emotions, memory, and motivation, not sleep.
Thymosin is a hormone that stimulates the development of T cells, which are part of the immune system.
Choice C is wrong because the circulatory system is the system of blood vessels and organs that transport blood throughout the body, not a part of the brain that controls sleep.
Dopamine is a neurotransmitter that is involved in reward, motivation, and movement, not sleep.

Cardiac output is calculated by multiplying the stroke volume by the heart rate, not by the systolic blood pressure.

Stroke volume is the amount of blood circulated by the heart with each beat. Heart rate is the number of beats per minute.

Systolic blood pressure is the pressure in the arteries when the heart contracts. Choice A is wrong because it confuses systolic blood pressure with heart rate.

Systolic blood pressure is not directly related to cardiac output, although it can be affected by it.

1: Cardiac Output- Definition, Factors Affecting, Cardiac Index - BYJU’S 2: Cardiac Output (Fick’s Formula) - MDCalc 3: Calculating how much blood is pumped by the heart - Cellular respiration and transport - Edexcel - GCSE Biology (Single Science) Revision - Edexcel - BBC Bitesize 4: Cardiac output - Structure and function of the heart - Higher Human Biology Revision - BBC Bitesize : Blood Pressure: What Is Normal? How To Measure Blood Pressure (healthline.com)