Although reptiles and birds have many differences in terms of movement, there are also many similarities in their bone structure and arrangement in each limb. This cladogram compares the bones from each animal, as well as the lobe-finned fish hypothesized to be the common ancestor of each animal. What conclusion can be drawn from the evidence presented in this cladogram?
a
Birds are more closely related to fish than to reptiles.
b
Birds and reptiles experienced a recent genetic drift, causing their speciation.
c
Birds and reptiles share homologous structures in their skeletons.
d
Birds and reptiles share the same DNA sequence.

the abdomen (less formally called the belly, stomach, tummy or midriff) constitutes the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. the region occupied by the abdomen is termed the abdominal cavity. the stomach secretes acid and enzymes that digest food. ridges of muscle tissue called rugae line the stomach. the stomach muscles contract periodically, churning food to enhance digestion. the pyloric sphincter is a muscular valve that opens to allow food to pass from the stomach to the small intestine.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)

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).