Hey All,
There seem to be enough issues here to merit my weighing in. Every time the thread settles on an answer, more questions arise!
If present metal prices continue to sharply rise, the value of the copper in a penny will soon be greater than the face value of the coin.
FIRST OFF. I agree entirely with parsifal. I don't believe this is a legitimate GMAT question. The subject of the verb "continue" is "present metal prices". Present metal prices aren't going to continue to rise. The price of metal might continue to rise (past its present value). This seems highly suspect as a logical construction. Of course, we don't have a choice here, so it's also a bit irrelevant.
(A) If present metal prices continue to sharply rise,
PROBLEM: Can't split an infinitive. Nothing goes between "to" and "rise". (Take that Jean-Luc Picard...)
(B) If present metal prices are continuing their sharp rise,
PROBLEM: Using the present progressive tense here is grammatically. When we use a conditional like "if", we should just use the regular present tense ("If BLAH continues to happen...").
(C) Should present metal prices continue their sharp rise,
ANSWER: Should is the same as if, signaling the conditional and requiring a simple present tense verb.
(D) Continuation of sharply rising metal prices should mean that
PROBLEM: "Should" here seems to be some kind of recommendation. Why should it mean that? Also, there should be an article in front of continuation ("The continuation").
(E) Metal prices’ sharp rise continuing should mean that
PROBLEM: Again, "should" seems to be a recommendation. Also "sharp rise continuing" is gramatically unsound, because it's unclear what it's modifying. Is "sharp rise continuing" one thing, or is it a "sharp rise" that is "continuing"? It's unclear.
Hope that helps!
-t