In which vs. what vs. where [closed]

Actually, the best choice would have been:

A Florida-based company, Netflow's growth seems to hinge on its international expansion as it is set to enter four Asian countries.

But that wasn't on offer.

How — and one use of what — can be eliminated because there is no way to parse the second clause of your sentence as an indirect question.

The Netflow executive explained how the firm was set to enter the market in four Asian countries.

The Netflow executive explained what it meant for the company to enter four Asian markets.

The other use of what as a relative pronoun carries the meaning “the thing(s) which” and within its clause always functions as direct object.

What your answer key says is utter nonsense.

The store didn't have what you wanted.

Again, there is no possible way to complete your sentence with "the thing(s) which" or for what to function as a direct object for set, an intransitive verb.

That leaves in which or where. Since one could construe expansion as a space in which entering four Asian markets takes place rather than the location where it is takes place, of the options given, in which seems the best.