Many rivers in central asia come from
a.
the heavy annual rainfall
c.
snowmelt from the mountains
b.
massive underground aquifers
d.
there are no major rivers in this region.

The answer is: "snowmelt from the mountains" .

c.  snow melt from the mountains

Explanation:

The source of water in the regions of the Central Asia forms the mountains and like the Amu Darya and the Syr Darya that fed Tajikistan comes to form the snow melting mountains and the glaciers and there are about 900 rivers system of the Tajikistan and are longer than 10 km. On east and south of central Asia the western Altai ad the presence of the high mountain ranges that extends into the Iran, Afghan and western china.  Also, most of the economic activity of central Asia is led by that of the agricultural system and thus the flow of the river is most important for these countries.

"pacesetter of the south," comma inside the quotes