Which is the FOURTH sentence of the paragraph?

Directions (Q. 131-135): Rearrange the following six sentences a, b, c, d, e and f in the proper sequence to form a meaningful paragraph; then answer the questions given below them.
a) Users can be asked to pay a small price for the protection of vital environmental features, and more areas for nature tourism can also raise revenues.
b) This would ensure that tigers and other animals are not isolated, and can disperse strong genetic traits to other populations.
c) The National Tiger Conservation Authority should insist on modification of existing roads to provide crossings for animals at locations identified in various studies.
d) An assessment by the Wildlife Institute of India states that tigers in at least 26 reserves face the destructive impact of roads and traffic.
e) A more robust approach would be to realign the roads away from all such landscapes.