Answer:
waxing and waning crescent
Explanation:
Beta-blockers decrease heart rate and blood pressure. Answer:D
It is a drug that might be used specifically to reduce heart rate in cardiac patients. The drug is also referred to as beta-adrenoceptor blocking agents and are prescription-only medicines (POMS).

In humans, the medulla region of the brain is mainly responsible for the regulation process of respiration. It is also called the respiratory rhythm centre. The chemosensitive area located near the respiratory centre sends signals across nerve impulses to alter the rate of expiration to eliminate compounds.
Answer: Subarachnoid
Explanation:
The space in the meninges below the arachnoid membrane and above the pia mater contains the cerebrospinal fluid. Cerebrospinal fluid is produced by choriod plexus( a cluster of capillaries) from the blood. Blood vessels traveling within the subarachnoid space deliver oxygen and nutrients to the spinal cord.
Minerals would be a reasonable explanation to this scenario
My opinion is on Minerals
Answer=Minerals