Some frogs have evolved to fertilize the eggs on land and carry the tadpoles with them. what is the main advantage of this system?
a. they can love in warm environments
b. they can live away from water
c. they can live in areas with low food
d. they don't need to find a mate

b. They can live away from water

Explanation:

The frogs are the amphibian organisms, which are capable of survival both in water as well as land. In frogs external fertilization is used as a mode of sexual reproduction. The females lay their eggs in water in the same time the males also secrete their sperms in the water. The eggs are fertilized by the sperms in water. For reproduction the frogs are dependent on water. But with the evolution of frogs, which allows them to fertilize the eggs on the land. The frogs can live away from water.

explanation:

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.