How many milliliters are in 1 liter?

One liter is defined as equal to 1000 milliliters. This relationship is based on the metric system, where the prefix "milli-" denotes a factor of one-thousandth. Therefore, when converting liters to milliliters, you multiply the number of liters by 1000. Since 1 liter equals 1000 milliliters, the correct choice clearly reflects this direct conversion. Understanding this basic metric conversion is essential, especially in nursing and healthcare settings where precise measurements are crucial for medication dosing and fluid management.