I have many question, please again help me to find the error in this sentence

Question

If the oxygen supply in the atmosphere was not replenished by plants, it would soon be exhausted.please explain why is it wrong and what is the correct?

 

 

thank you

Answer 1

Actually, many native speakers of English would say there is nothing "incorrect" with If the oxygen supply in the atmosphere was not replenished by plants, it would soon be exhausted, but the sentence does violate an older rule involving the use of the so-called subjunctive mood for verbs in clauses that express some condition or state that is contrary to fact. That is, the first clause in this sentence, which as signaled by the initial if indicates a condition, expresses a situation that is in fact not true, that is, the oxygen supply in the atmosphere actually is replenished by plants (and the following clause using the modal would before the main verb expresses the not-real resulting state, namely it would soon be exhausted, in other words, it, referring back to the oxygen supply, is not now exhausted). The subjunctive is thus used for the verb in the if-clause, and in older English the form were was used as the present-time subjunctive of the verb be with any subject, including third-person singular subjects like singular countable nouns such as supply in this sentence. Hence, the traditional, formal way to say the first clause here is If the oxygen supply were not replenished by plants . . . and this would account for the "error" in your sentence.

 

The trouble is that were of course shares exactly the same form as the indicative, i.e., non-subjunctive, past tense form of be for plural subjects (and also you with singular reference) whereas was is used for both singular subjects and I. And because be is such a commonly-used verb, English speakers are much more used to hearing, and thus repeating, I was, the supply was etc. in the normal, indicative use, while constructions that traditionally require the subjunctive are so relatively rare that it's natural for speakers just to substitute the more familiar was for were in cases where the later would be traditionally required or "prescribed," e.g., If the oxygen supply was not replenished . . . as in your original sentence or If I was Noam Chomsky, I would know everything about grammar (that is, I am not Chomsky despite what you might think from my brilliant answer here). This usage is so common now in all registers of English, even quite formal prose, that few people ever really call it out, but there are still some people who adhere to the older rule that says you "must" use were in all such sentences.