Which of the following is the best example of gene flow? a) an earthquake kills most individuals in a tree population, leaving just a few survivors. b) wind blows pollen from one population of plants to another, and cross-fertilization occurs. c) genes are shuffled by the crossing over of chromosomes during meiosis. d) a polyploid plant develops.

the answer is a or when it says crossing over

i believe the correct answer from the choices listed above is the first option. the scientists need to look at the   validity of data, claims, hypotheses, and observations before  developing an argument. they base their arguments on facts that are present and they make sure they have proofs. 

explanation:

the element that provides strength to the exoskeletons of clams and oysters is phosphorus.

this is so because calcium carbonate is the main component in the shells. calcium carbonate is strengthened by phosphorus.

explanation: