Molecular formula identification for C4H8O

Steps:

• Calculate expected formula for saturated alcohol: C4H10O (general CnH2n+2O).
• Compute degree of unsaturation: (2C + 2 - H - X + N)/2 = (10 - 8)/2 = 1, indicating one double bond or ring.
• Match choices to structures with exactly 4C, 8H, 1O.
• Verify A fits (e.g., butanal or cyclobutanol); others do not.

Why A is correct:

• Structure in A has 4 carbons, 8 hydrogens, 1 oxygen, matching C4H8O exactly per molecular formula definition.

Why the others are wrong:

• B: Formula is C4H10O (saturated, extra H2).
• C: Formula is C4H6O (unsaturated, missing H2).
• D: Formula is C5H8O (extra carbon).

Not enough information on exact structures, but assuming standard options.

Final answer: A