Multi-choice problem: Choose from the options at the end, and answer how do you do this: How can I know how much paint is in a tightly sealed can?

OPTIONS: a). After you finish painting, and before you close the paint can, paint a line across the label to show the paint level, that way you'll know how much and what color the paint is without opening it.; b). After you finish painting, and before you close the paint can, paint a line across the inside of the can to show the paint level, that way you'll know how much and what color the paint is without opening it.;
a).