The correct answer is nurturing.
To foster means to encourage the development of something or to bring up a child that is not one's own by birth.
Some synonyms of the word to foster are: encourage, promote, advance, forward, nurture, strengthen, endorse.
To nurture means to feed or protect, support or encourage, bring up, train, educate.
Relating to the FDA's challenge, both to foster and to nurture have the meaning of promote or advance, in this case promoting the child's development.
