In little more than a decade, argentina has become the world’s leading exporter of honey, with nearly 90,000 tons a year sold to foreign markets, almost half of which going to the united states. a. with nearly 90,000 tons a year sold to foreign markets, almost half of which goingb. with the sale of nearly 90,000 tons a year to foreign markets, and almost half of it that goesc. with the sale to foreign markets of nearly 90,000 tons a year, with almost half of it goingd. selling nearly 90,000 tons a year to foreign markets, and almost half of it goese. selling nearly 90,000 tons a year to foreign markets, with almost half going

Comma + present participle modifier is used to refer to the complete preceding clause - the modifier describes the result of the preceding clause or explains how the action in the preceding clause is done. Here the present participle "selling nearly" is required to describe how Argentina became the leading exporter. Thus option D and E are left. IN option D the pronoun "It" does not a valid antecedent. Hence E is the best option among the given.

However in option E, the prepositional phrase "with almost half going.." refers in turn to the present participle modifier "selling..." - such usage is generally considered awkward in GMAT. A better, more GMAT-like construction would be:

In little more than a decade, Argentina has become the world’s leading exporter of honey, selling to foreign markets nearly 90,000 tons a year, half going to United States.

OR

In little more than a decade, Argentina has become the world’s leading exporter of honey, selling to foreign markets nearly 90,000 tons a year, half of them going to United States.

OR

In little more than a decade, Argentina has become the world’s leading exporter of honey, selling to foreign markets nearly 90,000 tons a year, half of which went to United States.

The above three alternatives show the correct usage of three different forms of subgroup modifier (referring to "90,000 tons").