Your answer is B, C , and D.
Easy. Answer is oxygen because it says which one was missing before any life was on earth. And in order to have life on earth you need oxygen!
:)
<span>Homologous chromosomes exchange DNA during meiosis in a process called crossing-over. Crossing-over sometimes involves an unequal swapping of DNA. Basically one chromosome in the pair gets extra DNA.</span>
Carlos will have to consume about 63 gram of protein per day.
The dietary reference intake of protein is 0.8 gram of protein per kilogram body weight or 0.36 gram per pound. Carlos is 175 pounds in weight, so he is going to need 0.36 * 175 = 63. Thus, Carlos needs 63 grams of protein per day.<span />
C. Webbed feet. I'm pretty sure that's the answer lol