Rhizobium. ████████ ██████ ██ ███ █████ ██ ████ ██████ ██ █████ ███████ ███████ █████ █████████ █████ ██ ███ ██ ███ █████████ █████ █████████ ███ █████ ███ ██████████ ██████ ████ ██ ██████ ████████ ████ ██ ████████ ██ ████████████ ██ ██████████████ ███████████ ██ ██ █████████████ ████████ ██ █████████ █████ ███████ █████ █████ ████ ████ ████ ██ █████████ █████████ ███ ████ ███ ██████████ ███████████ ████ ██ ████████
This argument banks on the assumption that wheat is analogous to beans when it comes to hosting Rhizo. Here’s a summary:
Wheat needs nitrogen to grow. Currently, the only way we can give it nitrogen is via fertilizer. But check out these bean plants – they get their nitrogen from the Rhizo living inside them. If we could get Rhizo to live inside wheat, [we’d have another source of nitrogen, so]* we would need less fertilizer.
For this logic to work, growing Rhizo inside wheat must be substantially similar to growing Rhizo inside beans. Specifically, whatever it is about beans that makes Rhizo produce nitrogen needs to carry over to wheat as well.
Viewing the argument through this lens or something like it is pretty reasonable to achieve up front, but necessary assumption questions often demand process of elimination no matter what, so it’s fine if you don’t have this gap cleanly worded in your head when you move to the answers.
*That bit in brackets is an implicit premise – it’s a stepping stone that isn’t written out in the argument itself, but is essential to how the argument functions.
The argument above makes which ███ ██ ███ █████████ ████████████
Biotechnology should be ████████ ██████ █████████ ██████ ████ ██ ███ ███████ ██████████ ███████████
(A) fails when it introduces normative language (about what should be). All the argument’s claims are descriptive (about what is). These two categories are distinct, which in this case means our purely-descriptive argument certainly doesn’t make any normative assumptions.
Fixed nitrogen is █████████ ███ ████ ████ ████████ ████ ████ ██ ████████ ██ ██████████ ██████████ ███ ███████ █████ ██████
(B) negated: Wheat also needs other nutrients that require fertilizer.
That’s fine as long as our need for those other fertilizers doesn’t skyrocket out of nowhere. If our need for all the other fertilizers stays the same and our need for nitrogen-based fertilizers decreases, then our overall need for fertilizers will decrease.
There are no █████████ █████████ ███████ ██ █████ ██ █████ ███████ ████ ████ █████████ ████████ ██████ ██ █████ ██████
(C) negated: There are some naturally occurring strains of wheat or other grasses that do grow Rhizo.
There’s a relevant difference between naturally occurring strains of wheat and strains suitable for use as crops. These domains are distinct enough that facts about what happens in the natural world don’t meaningfully threaten this argument about the world of human agriculture.
Legumes are currently ███ ████ █████ ████ ███████ █████ ███ ██████ ██ █████ █████████
(D) negated: There are some non-legume crops that produce their own supply of fixed nitrogen.
The word “normally” in our argument makes room for the occasional exception. There may be some circumstances or individual strains that allow for a self-sustaining fixed nitrogen supply, but that leaves plenty of room for this biotech plan to increase that number dramatically.
Rhizobium bacteria living ██ ███ █████ ██ █████ █████ ███████ █████ █████████
(E) negated: Rhizo living in wheat roots would not produce fixed nitrogen.
That would be terrible news for our argument! Its whole theory is that we can recreate the magic of bean plants producing their own nitrogen via Rhizo. If we’re getting zero fixed nitrogen out of the deal, we’ll need just as much nitrogen-based fertilizer as always.