=== Model: grok-4.6-direct | Task: bench:gpqa_diamond | Rep: 1 ===
=== Score: 5/5 | Wall: 23.604s | Cost: $0.010294 ===
=== Pass: True | Finish: stop | In-reasoning-only: False ===

--- JUDGE ---
gpqa_diamond

--- RESPONSE ---
The standard reduction potential of oxygen is \(E^\circ=1.23\,\mathrm{V}\) in acid (\(\mathrm{O_2+4H^++4e^-\to2H_2O}\)) but only \(E^\circ=0.40\,\mathrm{V}\) in base (\(\mathrm{O_2+2H_2O+4e^-\to4OH^-}\)). The markedly lower potential means that oxygen is thermodynamically a weaker oxidant in basic solution.

The oxygen-reduction reaction itself, however, is known to be kinetically more facile in alkaline media than in acid (lower over-potential, possibility of using non-precious-metal catalysts, etc.). Consequently oxygen reacts more slowly in acidic solution.

The two blanks are therefore filled by “weaker” and “slower.”

The answer is (C)