What does leveling a balance ensure?

Leveling a balance ensures that the base is on a horizontal plane for accuracy. A properly leveled balance is essential for obtaining precise and consistent measurements. When the balance is level, it can accurately convey the force exerted by the sample's weight without being swayed by any built-in bias that might occur if the instrument is tilted. This adjustment helps to minimize errors caused by gravitational effects or inadequate contact points on the weighing pan, ultimately resulting in more reliable data for scientific experiments and analyses.

The other choices, while related to aspects of balance and weighing measurements, do not directly address the critical need to level the instrument for obtaining accurate readings.