Which Best Describes Dalton's Law

Which best describes Dalton's law?

A) In a mixture of gases, the partial pressure is equal to the sum of the total pressures of the separate gases.
B) In a mixture of gases, the total pressure is unequal to the sum of the partial pressures of the separate gases.
C) In a solitary gas, the total pressure is equal to the sum of the partial pressures of the separate gases.
D) In a mixture of gases, the total pressure is equal to the sum of the partial pressures of the separate gases.