Heavy metals are dangerous to humans because they a. inhibit important enzymes. b. cause apoptosis. c. reduce the body's ability to carry oxygen. d. break down mitochondria.

Heavy metals are naturally occurring elements that have a high atomic weight and density much greater than water. Some common heavy metals include lead, mercury, arsenic, and cadmium. In high amounts, these metals can be toxic and cause harm to the human body.

a. Inhibition of Important Enzymes: Heavy metals can bind to essential proteins and enzymes, disrupting their function and potentially leading to the malfunction or death of cells. b. Apoptosis: Apoptosis is programmed cell death, which can be caused by a variety of factors, including exposure to toxins or damage to the cell's DNA. c. Reduced Ability to Carry Oxygen: Toxins or damages to the body's hemoglobin can hinder its ability to bind, transport and release oxygen in the tissues and organs. d. Breakdown of Mitochondria: Mitochondria are the powerhouse of a cell and are responsible for generating most of the cell's energy. If the mitochondria are damaged, it can affect the cell's energy production and potentially lead to cell death.

The correct answer is a. Heavy metals are dangerous to humans because they inhibit important enzymes.