Trend in reducing power of hydrogen halides Steps:

• Identify that "ease of oxidation" for HX refers to the reducing strength of the X⁻ ion.
• Recall standard reduction potentials: E°(X₂/2X⁻) decreases down the group (F: +2.87 V > Cl: +1.36 V > Br: +1.07 V > I: +0.54 V).
• Lower E° means oxidation of X⁻ to X₂ is more thermodynamically favorable (ΔG = -nFE° less negative for reduction, so positive for oxidation).
• Thus, HI is easiest to oxidize, HCl harder, confirming ease increases down the group.

Why A is correct:

• Matches the electrode potential trend, where decreasing E° increases the favorability of oxidation per the Nernst equation.

Why the others are wrong:

• B: Claims increasing difficulty (decreasing ease), opposite to potential trend.
• C: States decreasing ease, contradicting increasing reducing power.
• D: "More difficult decreases" implies increasing ease but misphrases the property as difficulty rather than ease.

Final answer: A