Are electrons inside or outside the nucleus of an atom

Ineed to know why d is the correct answer asap

Which set of characteristics best describes sedimentary rock? a) largest type of rock, made of organic matter, hardest type of rock b) often contains layers, forms near sources of water, contains fossils c) least abundant type of rock, made of other rocks, made mostly of minerals d) most abundant type in earth's crust, made of magma/lava, contains no fossils

The negative impacts of nonnative species generally outweigh the positive impacts