Genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).
Multiple choices :
A. test for chemicals that might poison fish and cause algae to grow
B measure the dissolved oxygen content in pond-water samples
C look for sources of pollution that may be affecting the pond
D measure the amount of light at various levels in the pond
Answer;
D. measure the amount of light at various levels in the pond
Fish in the pond feeds on the algae that grows in the pod.
Therefore; death of fish in the pond caused a large increase in algae populations.
Measuring the amount of light in the pond would not tell the student what caused the death of the fish in the pond.
My best answer for you is:
An earthquake with a shallow focus and a magnitude of 4.5
Endoplasmic reticulum -> Golgi -> vesicles that fuse with plasma membrane.