I am confused about this problem. Any help is appreciated.

A chemist performs a series of reactions that produce binary lithium compounds. The elements include sulfur, chlorine, nitrogen, fluorine, selenium, oxygen, and iodine. The models below represent the ionic radii of compounds formed by reacting lithium with three of the elements.
a. Identify the three compounds that the models represent. Explain your answer. (2 points)

b. Write a hypothesis that the chemist might use when investigating another periodic trend of various elements. (2 points)

Here is the link to the model:
h ttps://www.google.com/search?q=solve:+6,+a+chemist+performs+a+series+of&safe=active&rlz=1C1CHBF_enUS720US720&sxsrf=ALeKk00zUK1oEC7s3gmwrAq4p1i1eFBuhw:1586638197227&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjBuofxn-HoAhUbK80KHY5OAp4Q_AUoAnoECAkQBA&biw=1366&bih=625#imgrc=QWTearlz5AjDdM

3 answers

What are three compounds?
I cannot choose a hypothesis for you. It is an estimate YOU choose
Are you taking AP Chemistry online. Me too. Did you get an answer to this question?
I don't get this one too, I'm taking AP chem online.