**Core Concept**
Half-life (t₁/₂) of a drug is calculated using the formula: t₁/₂ = (0.693 × Vd) / Cl, where Vd is the volume of distribution and Cl is the clearance. This formula applies to drugs following first-order kinetics, which is typical in phase I trials.

**Why the Correct Answer is Right**
Using the formula: t₁/₂ = 0.693 × Vd / Cl
Given: Vd = 80 L, Cl = 1.386 L/hr
t₁/₂ = (0.693 × 80) / 1.386 = 55.44 / 1.386 ≈ 40 hours.
This result reflects the time required for the drug concentration to reduce by half in Ram, based on his pharmacokinetic parameters.

**Why Each Wrong Option is Incorrect**
Option A: 83 hr – This is too high; it results from incorrect multiplication or miscalculation of the formula.
Option B: 77 hr – Incorrectly derived from a misapplied formula or arithmetic error.
Option D: 0.02 hr – This is far too low and implies extremely rapid elimination, inconsistent with the given clearance and distribution volume.

**Clinical Pearl / High-Yield Fact**
In phase I trials, half-life is critical for assessing drug safety and dosing frequency. A half-life of ~40 hours suggests very slow elimination, which may lead to accumulation and toxicity if not carefully monitored.

✓ Correct Answer: C. 40 hr