The fertilized egg begins a rapid descent to the uterus. The period of rest in the tube appears to be necessary for full development of the fertilized egg and for the uterus to prepare to receive theegg. ... At the end of this transition period, the embryo becomes a mass of very organized cells, called a blastocyst.
Royal colonies: Another term for provincial colonies; colonies that were under the direct control of the King, who usually appointed a Royal Governor. proprietary colonies: Owned by a person (always a white male) or family, who could make laws and appoint officials as he or they pleased.
Toxic Waste and Thermal radiation is a big one.
I'd say thermal radiation would be the ansewr.