Lakes and rivers constitute
a. 87% of freshwater
b. a tiny fraction of earth’s freshwater
c. a majority of earth’s freshwater
d. a majority of water on earth

(B) A tiny fraction of earth's freshwater

Explanation:

 Lakes and the rivers are mainly constitute of the tiny fraction of the earth freshwater. The water in the lakes and the river are mainly comes from the rain, streams, melting ice and the groundwater.

Approximately 2% of the freshwater are found in the lakes and the rivers which is present in the form of tiny fraction, the rest is the saline or the ocean based water. The 1% of the freshwater is easily found in the glaciers and the also in the snowfields only.

Therefore, Option (B) is correct option.