Independent variable = age Dependent variable = height
"depends on age" indicates that age is independent.
----------------------------------- Part (b)
Independent variable = amount of sleep Dependent variable = mood
The key word is "determines". The stuff before this word is the independent variable which affects the dependent variable. ----------------------------------- Part (c)
Independent variable = time water has been running dependent variable = amount of water in the tub
Time is usually the independent variable ----------------------------------- Part (d)
Independent variable = speed dependent variable = distance from home