Cracking of butane favors C2 + C2 products over C1 + C3 Steps:

• C4H10 is butane, cracked by thermal decomposition of C-C bonds.
• Central bond cleavage yields two ethyl radicals (C2H5•), leading to C2 products.
• Terminal bond cleavage (less likely) yields methyl (CH3•) and propyl (C3H7•) radicals, leading to C3 products.
• Ethyl radicals readily form C2H6 and C2H4; propyl forms C3H8 or C3H6 with extra steps.

Why D is correct:

• C3H6 requires unfavorable terminal bond break plus dehydrogenation of propyl radical (losing H•), per free radical mechanism.

Why the others are wrong:

• A. C2H6 from favored ethyl radicals via H abstraction.
• B. C2H4 from favored ethyl radicals via disproportionation.
• C. C3H8 from propyl radical via H abstraction, without extra dehydrogenation.

Final answer: D