Entrepreneurs attempted, but failed, to harvest nuts from plantations grown in Southeast Asia. Attempts to grow Brazil nut trees in South American plantations also failed. In both cases, the trees grew vigorously, produced healthy flowers in profusion, but set no fruit. Consequently, what is the likely source of the problem?
A) poor sporophyte viability B) poor sporophyte fertility C) failure to produce fertile ovules D) failure to produce pollen E) pollination failure