Why does nitroglycerin need to be kept in a dark, tightly closed bottle? a. exposure to air and light causes the drug to degrade. b. exposure to air and light increases the drug's potency. c. the effects of air and light have not been intensely investigated. d. exposure to air and light causes the drug to become unstable.

A.  

Nitroglycerin are best kept in a dark and tightly closed bottle to protect from exposure to air and light that causes the drug to degrade or reduce its strength. Only the original containers protect Nitroglycerin tablets from air, heat, moisture and light. Therefore, do not attempt to transfer it in a pill box.

Moreover,if the medication has been exposed to a high temperature, air and light, there is a tendency that its potency is lost and it should be discarded.  

i think your answer is a. coordination