Which of the following represents the left hand sum approximation of area under the curve y = f(t)?

O limₙ[infinity]→ [infinity]Σᵢ₌₀ f(tᵢ)Δt
O limₙ[infinity]→ ⁿΣᵢ₌₀ f(tᵢ)Δt
O limₙ[infinity]→ ⁿ⁻¹Σᵢ₌₁ f(tᵢ)Δt
O limₙ[infinity]→ [infinity]Σᵢ₌₁ f(tᵢ)Δt