This does not affect the argument. The author does not assume that replacing nylon with cotton fiber in thread and rope will solve all environmental problems. The persistence of many environmental issues despite this change does not weaken the argument.

This strengthens the argument. It reinforces the idea that replacing nylon with cotton fiber in thread and rope would reduce environmental damage by suggesting that environmental benefits could be seen even if only some of the nylon is replaced with cotton fiber.

This weakens the argument by making it unclear whether replacing nylon with cotton fiber in thread and rope would have a net positive effect on the environment. If this switch increases nylon production and thus, nitrous oxide emissions, the environment may actually be worse off.

This strengthens the argument. If nylon is replaced with cotton fiber in thread and rope, the levels of several other pollutants in addition to nitrous oxide would decrease. This reinforces the idea that the switch would reduce environmental damage.

This does not affect the argument. (E) says the production of cotton fiber would increase faster if cotton fiber replaced nylon in thread and rope, which does not have any impact on the argument.