If NASA's Cassini mission successfully completes its next phase – orbi

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I thought E change the meaning but it turns out that C and D are wordy.

When we 'continue,' we extend what was, has been, or have been already. Therefore, to mention both in the same clause is plain redundant. A, B, C, and D all suffer this malady. E is the answer

This sentence presents an if/then situation. The if part is a hypothetical situation in the future. Therefore, the then part must be a future result. However, the underlined portion uses "have been," inexplicably shifting to the present perfect tense.

(A) and (B) begin with the present perfect tense verb "have," while (C), (D), and (E) use the future tense verb "will."

There is no reason to refer to the past. Everything here is predicting the future (If the mission is successful, people will be enthralled). That eliminates (A) and (B).

The remaining choices all use the future tense, but (C) and (D) unnecessarily add an extra phrase. If it's said that something "will continue," it's already implicit that this action has happened before. (After all, how can something continue if it's never happened?) So, there's no need to add a past ("already did") or present perfect ("have already") phrase to this prediction. That eliminates (C) and (D).

That leaves (E) as the correct answer. (E) creates a sentence that deals entirely with possible future actions.

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If NASA's Cassini mission successfully completes its next phase – orbiting Saturn many times over a several-year period – its stunning photos of and data concerning Saturn have been and will continue to enthrall astronomers throughout the world.

If we take a closer look at the prompt above, we get to realize that the main "Nasa's mission" event is an event that is set to occur in the future. Hence, it makes to sense to refer to this future event with any verb that is used to describe past tense events (verbs such as have/had/did). In (B), (C), and (D) we have different verb forms that introduces a past tense form into the overall structure of the prompt. This (for reasons explained earlier in this paragraph) is wrong. For that reason, we can eliminate (A), (B), (C), and (D)


E. will continue to enthrall - (E) is therefore your correct answer