Should present metal prices continue their sharp rise, the value of th

I am responding to a request from kinjiGC.

First of all, let me say: this is NOT a high quality GMAT-like SC question!! If I were going to give this question a grade, I would give it a grade of a C. It's not the worst it could be, but it is far from stellar.

Choices (D) & (E) are ridiculous incorrect: they are take-them-out-back-and-shoot-them wrong. Incorrect answer choices on the real GMAT are typically a little more tempting than these.

Choice (B) is wrong, because the use of the present progressive is unjustified. This is a legitimate and GMAT-like incorrect answer choice.

Choice (C) is considered incorrect purely because of the split infinitive. This is tricky. On the one hand, it appears that the GMAT disapproves of the split infinitive, as many sophisticated writers do, present writer included. On GMAT SC, split infinitives only appear in incorrect answer choices. I have never seen an official question with a split infinitive in the correct answer choice. On the other hand, the GMAT never uses a split infinitive as the sole deciding split that eliminates an answer choice. Wherever a split infinitive appears, there is always some other, more obvious grammatical mistake that eliminates the answer choice: the split infinitive itself is never the only deciding factor. Thus, choice (C) is a particularly un-GMAT-like wrong answer.

This leaves us with the OA of (A). Is (A) correct? Yes, 100% correct. This is a particularly sophisticated structure, a hyper-fancy way to state a conditional. I don't know that I have ever seen this sophisticated structure used on an official question, but it is common in very high quality writing. The use of "should" is a very fancy way to frame a conditional.

Ordinary: If you get home before I do, light the stove.
Fancy: Should you get home before I do, light the stove.

Factual: If you a fan of opera, you will enjoy this novel.
Hypothetical: Should you be a fan of opera, you would enjoy this novel.

You will notice: the construction is not the factual "if-then" construction of a general rule. This construction, like many in the subjunctive, carries the connotation of something contrary to expectation. In the second statement, I am not at all sure that my addressee is a fan of opera, and I am speaking more hypothetically. Much in the same way, the speaker in the practice sentence above is not sure whether metal prices will continue their sharp rise: the speaker is speculating, speaking hypothetically about an unknown future.

Once again, you will see this construction in sophisticated writing, but I do not remember a single question in which "should" is used this way.

My guess is that this particular SC question was written by somebody particularly well-spoken who was more or less clueless about the standards the GMAT maintains. Obviously, this does not produce a high quality question. A high quality GMAT practice question can only be produced by someone who is well-spoken and who knows the standards of the GMAT intimately.

Here is a high quality GMAT SC practice question:
https://gmat.magoosh.com/questions/3273

Mike