Which of the following statements is true?

a.

the nitrogen cycle is the most important cycle for life.

b.

the oxygen cycle is the least important cycle for life.

c.

life can be sustained without any of the cycles for life present.

d.

all cycles of matter are equally important for life to be sustained

Explain how scientists use geologic time to determine the age of landforms.

Scientists discover two populations of mice on either side of a major river. the two populations have almost identical genes but the mice from one side cannot breed with mice from the other. this is most likely because

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit.there is a precise compatibility between the active site and the lactose molecule.specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.