Q1. What is the differentiation of the subterranean root?

In a discussion of plant move from water to land, what is the differentiation of the subterranean root? Someone please help me with a “layman’s” explanation!

Q2. In spite of their best efforts, hospitals seem to be unable to reduce their nosocomial infection rate to zero. What are some reasons why there will always be some nosocomial infections?

Q3. Fluorine has an atomic number of 9 and a mass number of 19. How various electrons are needed to complete valence shell of a fluorine atom?