Sometimes doctors inject medicines directly into the bloodstream. in which blood vessel do they inject? why?

Doctors inject medicines in veins because veins are more accessible and donot have high pressure due to which there is no risk of blood backing up with into the infused fluid.

However there are some cases when medicine is injected in artery but a lot of precautions needs to be taken while doing so.

Only algae, oak trees, and bermuda grass produce atp by photosynthesis i am almost positive