Answer: Option A
:
A
The question asks for the factor best denoting the case of Rwanda and Haiti.
From the second paragraph, “…one strand consisted of population growth outstripping available resources: a dilemma similar to the one foreseen by Thomas Malthus in 1798 and being played out today in Rwanda, Haiti, and elsewhere. As the archaeologist David Webster succinctly puts it, "Too many farmers grew too many crops on too much of the landscape. Compounding that mismatch between population and resources was the second strand: the effects of deforestation and hillside erosion, which caused a decrease in the amount of useable farmland at a time when more rather than less farmland was needed, and possibly exacerbated by an anthropogenic drought resulting from deforestation, by soil nutrient depletion and other soil problems, and by the struggle to prevent bracken ferns from overrunning the fields”.
The keywords are the words "limited”, "land" and "resources”. The second strand continues in the same vein and says that land and resources were limited. Combining the two, option (a) is the right answer option. Option (b) talks about “land resources” but does not mention other resources which were also scarce. Options (c) states" ethnic groups fighting with each other” but there is no mention of fighting in the passage. Option (d) mentions "ethnic groups competing for political power". There is no mention of this in the passage as well. Hence option (a) is the correct answer.