How many mL are in a liter?

One liter is equivalent to 1000 milliliters. This is based on the metric system, where the prefix "milli-" denotes a factor of one-thousandth. Therefore, since there are 1000 milliliters in a liter, the correct answer reflects this standard measurement unit conversion. Understanding this relationship is fundamental in nursing and healthcare practice, as accurate dosage calculations often rely on these metric conversions to administer the correct amounts of medications and fluids.