In virtually all types of tissue in every animal species, dioxin induc

I respectfully disagree with your assessment of the grammatical usage of or, AjiteshArun, and whether my own view is correct or incorrect, I would like the entire community to understand the logic behind why I would say so. According to Dictionary.com, an admittedly American source, there are six ways in which or may be used as a conjunction. When it is used to introduce another option, that second option is not contained within commas. The double commas make all the difference in intended meaning. Consider the following examples:

1) The police are trying to ascertain whether Tony or the magician committed the crime.
In this sentence, there are two suspects, Tony or the magician. The magician is the other option, fitting the first definition of or from the source I cited.

2) The police are trying to ascertain whether Tony, or the magician, committed the crime.
In this sentence, there is a single suspect, Tony, who may have been dressed as a magician (for whatever reason) or known as a magician. The magician is not another option, unless the sentence is going back against itself, but is instead an alternative form of the same noun, fitting the second definition of or.

Getting to the point, in the sentence at hand, or render harmless is contained within double commas in every answer choice, so we cannot even suggest that one version is better than another on those grounds. If or were being used to introduce another option, then I would expect the answer to read,

(E) attempt to metabolize or render harmless the chemical irritant

I would have no qualms about such a sentence, nor would any grammarian or linguist I know. Now, like you, I am not an expert in biochemistry, and dioxins and such are beyond my ken, nor would I make the argument that metabolism and the act of rendering an irritant harmless were synonymous. But in terms of the grammatical structure of the sentence at hand, since the double commas are compulsory, I can only stand behind two potential uses of or, per the definitions I have been referring to all along:

"2 used to connect alternative terms for the same thing
the Hawaiian, or Sandwich, Islands.

"4 used to correct or rephrase what was previously said
His autobiography, or rather memoirs, will soon be ready for publication."

There is one more possibility that I should consider. There could be a difference between American and British English that I am unaware of that could account for the different perspectives. If so, would you please make me aware of some source material (perhaps the OED) that would back up your interpretation?

Thank you. As I like to say, this is all in the interest of helping the community better understand this test. My quarrel is not with you--I respect what you have to say, end of story--but I do take issue with unsubstantiated opinions when they come from Experts, since such opinions can lead readers astray.

- Andrew