What is the result of converting 19 liters into milliliters?

To convert liters into milliliters, it's essential to know that 1 liter is equal to 1,000 milliliters. Therefore, to find out how many milliliters are in 19 liters, you multiply 19 by 1,000:

19 liters × 1,000 mL/liter = 19,000 mL.

This calculation demonstrates that 19 liters is equivalent to 19,000 milliliters, making the correct answer A. Understanding this conversion is fundamental in measurements, especially in scientific contexts where precise quantities are often necessary. The other choices reflect incorrect conversions, perhaps due to forgetting to multiply by 1,000 or miscalculating.