atoms combine when

a. the number of protons and neutrons is the same
b. their electrons are shared or transferred
c. the number of electrons and protons is the same
d. their outer electron shells are filled

the answer is atoms combine when their electrons are shared or transferred

hope this helps

it has to be b, about 97 percent.

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.