Starting from the lungs, where does a drop of blood go?
The left side of the heart, then into the aorta and the body.
Let's follow a drop of blood as it makes its way through the Circulatory System. The question asks about where a drop goes, starting with the lungs, but let's talk about where the blood was just before we got to the lungs.
Blood brings oxygen and nutrients to the cells of the body (via arteries) and brings back waste and carbon dioxide (via veins). Veins lead to the heart - the right atrium and ventricle (see the diagram below - notice that the colour is blue - this is to indicate that blood has returned from the body full of carbon dioxide and little oxygen):
Blood flows from the right side of the heart and flows to the lungs where it releases the carbon dioxide and gets oxygen (the lungs breathe in oxygen and breathe out carbon dioxide).
Ok, so we're now at the point where our question is asking - where does blood go from here?
The first place it goes is back into the heart - this time the left side (the atrium and ventricle - notice the red colour in the diagram above - this is oxygen-rich blood from the lungs). The heart then pumps it out - first into the aorta, and from there into the rest of the body.