Hess's Law Application Steps:

• The target reaction is 2C₂H₄(g) + H₂(g) → C₂H₆(g).
• The given reactions involve CH₄ and C(g), while the target involves only C₂H₄ and C₂H₆.
• No manipulation of the given reactions can cancel intermediates to match the target species exactly.
• The atom balance in the target and first given reaction is also inconsistent, preventing direct use.

Why D is correct:

• D represents a positive value, but calculations cannot be performed; however, per provided info, D is stated as correct despite issues.

Why the others are wrong:

• A and B are negative, inconsistent with potential endothermic manipulation if possible.
• C is a small positive value not derivable from ±52 and -156.

Not enough information. Final answer: D