Correct answer:
"<span>B- homologous chromosomes join together to form tetrads during prophase I"
</span>It is during prophase I that homologous chromosomes join together (<span>synapsis)</span> and form tetrads - four chromatids are together in the new structure of two chromosomes - and this is the reason why crossing-over occurs in this phase. It is in this tetrad that both arms of both chromosomes may crossover and matching regions exchange places. This process results in homologous chromosomes recombination leading to genetic variability.
C) Eutrophication is the answer
Have a Nice Day! :)
Solving problems with science means that to solve the problem the scientific method is used. This method includes observing, research, hypothesis , test and conclusion with a help of lot high level theory.
Without science there is not strict process to follow in order to resolve the problem end get to a solution.