15. Explain how a syringe draws; (a) injectable drug from a bottle.
(b) blood from a patient's body.

A. Tap the syringe with your finger to move air bubbles to the top. Then push gently on the plunger to push the air bubbles back into the vial. If you have a lot of bubbles, push the plunger to push all the medicine back into the vial. Draw medicine out again slowly and tap air bubbles out.

B. A syringe is just a hollow tube with a plunger at one end. After the needle is inserted into the vein (usually), the plunger is moved distally from the needle end, (pull the plunger back), and a negative air space is created that has less pressure that the vein.
The blood will, like water, find it’s way to the easiest escape route, i.e., the hollow tube, and the blood will flow into the syringe.

Im awfully sorry but i believe they taught you about mexico and there's a few things i dont know about them, but i could do this question if you provided those details.

Bolsa can be referring  to any type of bag,