Which of the following is not true about an explanatory variable?

a) it is used to explain changes in values of another variable
b) it is used to predict changes in values of another variable
c) it is plotted along the x-axis
d) it is a dependent variable

Answer asap and if you do you will get brainliest. catherine buys a gallon of ice cream from the store. after taking it home, she eats a fifth of a gallon of ice cream. her sister eats some of the ice cream as well. if two-thirds of the original amount of ice cream is left, then what fraction of a gallon of ice cream did her sister eat?