Scientists use tissue cultures to study possible medicines that can be used to treat cancer patients. What is one benefit of this procedure? Patients do not receive harmful or ineffective medication.
The cultured cells are not in their normal environment.
Doctors know how to treat all types of cancer.
One tissue culture can be used for all cancer patients.

A. Patients do not recieve harmful or ineffective medication.

Explanation:

Scientist use tissue cultures to study possible medications for the patients so that the patients aren't put in harms way to test a drug that would not work or be harmful.

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.