Not enough information to predict exact time

Steps:

• Identify block dimensions: 5 mm × 10 mm × 15 mm.
• Determine relevant diffusion distance: half the dimension perpendicular to diffusion path (varies by direction; smallest half = 2.5 mm, largest = 7.5 mm).
• Apply Fick's law: time t ≈ (distance)^2 / (2D), where D is dye's diffusion coefficient in agar (not provided).
• Without D or experimental rate, numerical prediction impossible; choices suggest possible calculations but lack basis.

Why A is correct:

• Cannot confirm; assumes unstated D yielding t = 6.2 s for 2.5 mm distance, but no formula or value given.

Why the others are wrong:

• B: Might assume 5 mm distance, but unverified.
• C: Might assume 7.5 mm distance, but unverified.
• D: Speculative without max time calculation.

Final answer: Not enough information.