补充22-13-2

Desertification, the creation of
desert-like conditions where none had
existed before, is the result of the vagaries
of weather and climate or the
mismanagement of the land or, in most
cases, some combination of both. Such
ecological deterioration in the Sahel has
been linked in several ways to the increased
size of livestock herds. During the fifteen
years preceding 1968, a period of extremely
favorable rainfall, the pastoralists moved
into the marginal regions in the north with
relatively large herds. However, with the
onset of a series of dry years beginning at
the end of the rainy season in 1967, the
pastoral populations found themselves
overtaxing very marginal rangelands, with
the result that the nomads viewed
themselves as victims of a natural disaster.
The mistaken idea that drought is an
unexpected event has often been used to
excuse the fact that long-range planning has
failed to take rainfall variability into account.
People blame the climate for agricultural
failures in semiarid regions and make it a
scapegoat for faulty population and
agricultural policies.

According to the passage, which of the following contributed to the desertification of the
    Sahel?
     I.      The size of the livestock herds grazing on the land
     II.     The quality of the land in the Sahel
     III.   The amount of rainfall after 1967
     (A) I only
     (B) II only
     (C) III only
     (D) I and III only
     (E) I, II, and III

Here, the key is E. But how can we get the hint of II " the quality of the land in the Sahel" from the first paragraph?

So confused!  哪位好心的人帮我看看吧！谢谢！