Long-term exposure to stress can damage the cardiovascular system by causing a) excessive electrical activity in heart muscle. b) sudden, dangerous increases in the heart rate. c) heart valve malfunction. d)chronic high blood pressure.

Sudden, dangerous increases in the heart rate.

Explanation:

Stress is a normal part of life. Stress can come from physical causes like not getting enough sleep or having an illness. Stress can also come from less dramatic causes like everyday obligations and pressures that may make anyone feel that nothing is in control. Depression and anxiety can increase your risk of dying from heart disease. Research suggests that long-term anxiety or emotional stress can increase the risk for sudden cardiac death.

the dna molecules have a negative charge because of the phosphate groups in their sugar-phosphate backbone, so they start moving through the matrix of the gel towards the positive pole. power is turned on and dna fragments migrate through gel (towards the positive electrode).

explanation:

nb

explanation:

kj