IMO E.

Because it is very obvious and coming straight from the argument; while other aren't.

Hi,

The conclusion is that the need for artificial fertilizers will be reduced

If you choose B, then if biotechnology succeeds, then you eliminate the need for artificial fertilizer because nitrogen is the only soil nutrient.

The point with E is that the argument does make the assumption that the bacteria will produce nitrogen to mirror the same effect it has on the legumes.

These are classic options for the negation test.

Regards
Anup

There are some tips that you can apply to these answer choices:

First, remember that an assumption question is very much like an inference question in terms of the answer choices. You generally want limited answer choices that stick to the the stimulus.

Look at choice A, This tells us what biotechnology "should" do. Should is a command. Does the stimulus make a command? No. So the answer choice cannot do this either. In the stimulus we are talking about what does happen or what will happen not what should happen.

Choice B, "nitrogen is the ONLY soil nutrient that must be supplied but artificial fertilizer"... ONLY is a tough word on Assumption questions as is ALL. In this question you are simply trying to conclude that the amount of fertilizers can be reduced. Does that mean that you need to prove zero fertilizers? No. You only need to reduce the fertilizers. It is like saying that if you grow your own beans you can save money on food. This does not mean that you only eat beans! Watch out for absolutes on assumption questions. They may occasionally be correct but they require a really high level of proof.

Choice C "There are NO naturally occurring strains" with Rhizobium bacteria. Why would this be required? Maybe there are natural strains that have not been discovered. Or the natural strains are not suitable for growing on a large scale. The point is that we are not talking about natural strains here.

Choice D This one also has the ONLY word. Do we need "Legumes to be the only crops that produce their own supply of fixed nitrogen"? Of course not. They could just happen to be what is used for this project.

Choice E has none of these obvious flaws. And it is necessary that the bacteria actually fix the nitrogen as proposed.

I wrote an article a while ago about inference questions called "who needs a stimulus?" It is about what I call "self-proving" answer choices. https://www.beatthegmat.com/mba/2012/01/ ... -questions

On this question if there was no stimulus I would put money on choice E because the other choices have classic flaws that you should look for in assumption answers.