Rift valleys can form when fractures in the Earth's crust widen. The valley walls slowly move at a rate of only a few millimeters a year. Which of these best describes the types of tectonic activity that forms rift valleys? a.)
b.)
c.)
d.)

c.) Rift valleys form where two plates move away from each other.

Explanation:

c.) polymerase chain reaction

- "unlike the original dna fingerprinting method, dna profiling does not use restriction enzymes to cut the dna. instead it uses the polymerase chain reaction (pcr)? to produce many copies of specific str sequences. pcr is an automated procedure that generates lots of copies of a specific sequence of dna."

because the light is a great source of energy for the plants to survive. (i hope this )