If land was cleared 100 years ago for farming and has recently returned to its natural state, covered with plants and trees, what has taken place?
a. evolutionary succession
b. ecological succession
c. primary succession
d. secondary succession

If the land was cleared 100 years ago for farming and has recently returned to its natural state, covered with plants and trees. Thus secondary succession has taken place.
Secondary succession is a series of community in which ones was colonized but later on become a damaged habitat. Then renewed 

Your answer is b i hope this