The main vent is the main outlet for the magma to escape. Secondary vents are smaller outlets through which magma escapes. The crater is created after an eruption blows the top off the volcano
Im pretty sure the answer to your question is d
The Panama Canal because it makes the most money and is the most important out of all the four.
Both are igneous rocks, but whereas volcanic rocks are formed from cooling lava on the surface, plutonic rocks are formed from cooling magma below the surface. So plutonic rock is an igneous intrusive rock, while volcanic rock is extrusive.
