Answer:
b. Gradual evolutionary change explains why organisms are well-suited to their environments.
Step-by-step explanation:
Darwin and Larmack are both evolutionists who believed that the present organisms or offspring are descendants of previous organisms. And they are able to survive till today from previous generation because they have certain features that make them resistant to selective pressure in their environment. Lamarck called concluded that changes in the physical features of the present organisms from using a certain body part more than others in order to survive is the major reason for their existence and resistant to selective pressure. He called his theory Law of use and disuse .
Darwin believed that, the ability to survive by theses organisms was due to certain factor or trait(gene) which the descendants must have inherited from the previous generations,. And these trait(gene) made them to resist selection pressures,and therefore have higher competition for survival than other organisms which lack these traits. Thus he concluded that nature must have selected these organisms with certain traits(genes) than others, He tagged his findings theory if evolution by natural selection.
However both scientists believed that present organisms are products of Gradual evolutionary changes of million of years ago.