Three Resistors Connected in Parallel Each Carry Currents Labeled I₁

Three resistors connected in parallel each carry currents labeled I₁, I₂, and I₃. Which of the following expresses the value of the total current I_T in the combined system?

A) I_T = (1/I₁ + 1/I₂ + 1/I₃)
B) I_T = I₁ = I₂ = I₃
C) I_T = I₁ + I₂ + I₃
D) I_T = (1/I₁ + 1/I₂ + 1/I₃) ^{- 1}