Although Cara has been obese for as long as she can remember, she is determined to lose excess body weight with a low-calorie diet. Cara is most likely to have difficulty becoming and staying thin because .
a. muscle tissue is maintained by fewer calories than is fat tissue.
b. low-calorie diets trigger increased secretions of PYY.
c. her resting metabolic rate will increase and prompt her to overeat.
d. if her body perceives starvation it will adapt and burn fewer calories.
e. she may have a higher-than-average set point for body weight.

Viruses use the host's machinery to make copies of themselves. however, some human viruses require a type of replication that humans do not normally have. for example, humans normally do not have the ability to convert rna into dna. how can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires? a) the virus causes mutations in the human cells, resulting in the formation of new enzymes that are capable of performing these roles.b) the viral genome codes for specialized enzymes not in the host.c) the virus infects only those cells and species that can perform all the replication roles necessary.d) viruses can stay in a quiescent state until the host cell evolves this ability.