A marathoner's leg muscles often feel heavy and prone to cramping after 20 or more miles. Which of the following is the best explanation for this?
O A marathoner's circulatory and respiratory system cannot take in sufficient oxygen, and the
muscle cells must switch to anaerobic respiration for energy.
O A marathoner's muscle cells contract when glucose reacts with oxygen.
O A marathoner's circulatory system takes in too much oxygen during a race, which causes
muscle cramping.
O A marathoner's muscle cells cannot store glucose for use as energy.

What is a codon and where is it found

In 2001, records showed that local stocks of fish were down worldwide. yet, records of harvests indicated that fish were being taken at records rates. what was actually happening?

Cladistics is a way of classifying organisms by examining the characteristics of their ancestors and descendants and depicting the relationships in a cladogram. which of the following best describes a challenge in classifying organisms this way? a. there are millions of species on earth, and a cladogram is not a practical means for classifying all of them. b. it is impossible to tell which organisms are most closely related to each other using a cladogram. c. cladograms are detail-oriented and do not provide a useful understanding of evolutionary relationships. d. there is a limited number of ways to organize the information, so most cladograms end up looking very similar.