GMAT Critical Reasoning (CR) | Re: Animals with a certain behavioral disorder have unusually high level o

Animals with a certain behavioral disorder have unusually high level of aluminum in their brain tissue. Since a silicon-based compound binds to aluminum and prevents it from affecting the brain tissue. Animals can be cured of the disorder by being treated with the compound.

The argument is based on which one of the following assumptions?

(A) Animals with the disorder have unusually high but invariable levels of aluminum in their brain tissue.
(B) Aluminum is the cause of the disorder rather