Two Thin Lenses Have Powers P₁ and P₂,measured in Diopters

Multiple Choice

Two thin lenses have powers P₁ and P₂,measured in diopters.If these lenses are placed in contact with one another,the resulting power is

A) more than both P₁ and P₂.
B) less than both P₁ and P₂.
C) half-way between P₁ and P₂.
D) P₁ + P₂.