One reason many waterfowl die each year of lead poisoning is because

Not able to understand why is "for the reason" not logical, but my bet is that between C and D, D is changing the meaning of the sentence.

C sheds only one of the reasons for the death of waterfowls. D on the other hand conveys that ingesting spent shotgun pellets is the SOLE reason for the deaths. But i'm not sure what is the intended meaning of the sentence?

EDIT -- Understood. "for" needs to be followed by the "cause". For is synonymous with "reason" so there is no need to repeat it.

One reason many waterfowl die each year of lead poisoning is because they often ingest spent shotgun pellets.

In most cases, the answers choices incorrectly and illogically state "the reason... is because" instead of actually explaining what the reason is. "Reason..because" is more or less stating why the reason exists.

These answer choices make that mistake
(A) One reason many waterfowl die each year of lead poisoning is because
(B) One reason why many waterfowl die each year of lead poisoning is because

In D, the sentence illogically communicates that the waterfowl die for a particular reason. As if they are dieing for a cause. E commits a similar mistake.
(D) Many waterfowl die each year of lead poisoning for the reason that
(E) Many waterfowl die each year of lead poisoning because of the reason that

C clearly communicates that the waterfowl die each year and that the reason that they die is X
(C) One reason many waterfowl die each year of lead poisoning is that

I eliminated C because there was nothing between 'one reason' and 'many waterfowl..'

Shouldn't it be 'One reason why xyz happens is that....' ?

Hello An78w,

We hope this finds you well.

To answer your query, no; the noun "reason" need not be accompanied by the term "why"; in fact, in this case, the use of "why" alongside "reason" is redundant.

We hope this helps.
All the best!
Experts' Global Team

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