The picture below shows a soil texture triangle.

Referring to the given diagram, we will find that the percentage of sand in silt is given on the base of the triangle.
The amount of sand is almost 50% of silt. Representing this on the percentage line, we will find that the percentage of sand is somewhere between the 40% and the 60%.

Based on the above, the best choice would be:
c. 40 percent to 60 percent