Which type of molecule stores the main source of energy used by animals?
a.) lipids
b.) proteins
c.) glycogen
d.) starch

c.) glycogen

Explanation:

Glycogen is a polysaccharide which is stored as an energy molecule in animals, bacteria and fungi. It is formed by a chain of glucose molecules. The average chain length varies from 8 to 12 glucose units. The glucose units are linked together by α (1-4) glycosidic linkage. The glycogen breaks down into glucose units so as to provide energy to the cells for performing various metabolic functions.  

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.