Question

select the two prepositional phrases. a british biotechnology firm is experimenting with genetically modified mosquitoes to combat dengue fever, a mosquito - borne illness that threatens the lives of millions.

Explanation:

A prepositional phrase starts with a preposition and ends with a noun, pronoun, gerund, or clause. In the given sentence, "with genetically modified mosquitoes" starts with the preposition "with" and "of millions" starts with the preposition "of".

Answer:

"with genetically modified mosquitoes", "of millions"