Piaget’s research revealed that children can learn to count long befor

Here's the official explanation provided by the GMAC for this question:

This sentence indicates that one milestone in children’s development occurs earlier than another such milestone. The original version expresses the earlier milestone in terms of what the children can do (children can learn to count). That version inappropriately contrasts the time when they are able to learn to count with a later condition (the recognition that … ). However, the most likely intended meaning is that the ability to count develops earlier than the ability to recognize the fact about quantities mentioned later in the sentence. This can be clearly and concisely communicated by making the reference to the second ability parallel with the reference to the first: can count … before they can recognize ….

Option A: This is unclear in drawing a contrast between the time when children can do something and the time of a specific act, event, or condition (the recognition).

Option B: Correct. This is grammatically correct and rhetorically effective. The parallel verb phrases can learn and can recognize express a clear relationship.

Option C: Can … before they would does not make good sense. The indicative mood of can is incompatible with the subjunctive would. The sentence would convey a clear and coherent meaning if would were changed to can, or even if would were simply omitted.

Option D: The verb form could means either were able to or would be able to. Neither of those meanings is appropriate to this context. The sentence would be best if the verb in this part of the sentence were parallel with can in the previous part; the relationship is between the time when children can do one thing and the time when they can do another thing. Using the recognition of instead of the recognition that makes this ungrammatical; the verb remains has no subject.

Option E: The verb in this part of the sentence should be parallel with can in the previous part; the relationship is between the time when children can do one thing and the time when they can do another thing. Using the recognition of instead of the recognition that makes this ungrammatical; the verb remains has no subject.

The correct answer is B.

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