What is the correct way to complete the text below? "American Field Service, one...

Questão de Inglês da banca Marinha aplicada no concurso ESCOLA NAVAL (2013). Confira a resolução completa abaixo:

What is the correct way to complete the text below?

"American Field Service, one of (1) ____ Exchange programs, said it saw a 6 percent increase in the number of families willing to host students next year."