cancer cells lack what is called contact inhibition which CAUSES them to continue to multiply without proper regulation in relation to the surrounding tissue cells. They also actually have a trait that draws blood directly to their tissue allowing them to grow easier. Furthermore, and lastly, they lack apoptosis which is programmed cell death that normal tissue cells undergo. All these are the underlying reasons why they continue to multiply and metastasize. THE ANSWER IS C
It is a Chemical reaction taking place un a solution in which one or more of the products is insoluble in the solvent, and so forms solid particles that fall to the bottom of the reactor
