As a result of the ground-breaking work of Barbara McClintock, many scientists now believe that all of the information encoded in 50,000 to 100,000 of the different genes found in a human cell are contained in merely three percent of the cell's DNA.

a) ...
b) 50,000 to 100,000 of the human cell's different genes are contained in a mere
c) the 50,000 to 100,000 different genes found in human cells are contained in merely
d) 50,000 to 100,000 of human cells' different genes is contained in merely
e) the 50,000 to 100,000 different genes found in a human cell is contained in a mere

OA is E

I have two questions for this SC.
- What is the difference between "50,000 to 100,000.... " and " the 50,000 to 100,000..."
- Why is mere preferred over merely