You try to help her form a new habit. (it takes 21 days to form a new habit)
I would say 1,2,&4 because bones cant protect organs from bacteria or sunlight.
You can think of independent and dependent variables in terms of cause and effect an independent variable is the variable you think is the cause, while a dependent variable is the effect. In an experiment, you manipulate the independent variable and measure the outcome in the dependent variable.
Hope this helps