The earth is populated mostly by single-celled organisms, such as bacteria. however, there are many multi-celled organisms as well. which of the following is a multi-celled organism? a. flower b. human c. insect d. all of these

all of them because it was a study island question and i got it right

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.