Determining molecular formula from skeletal structure

Steps:

• Count carbon atoms: the main chain and branches show 4 C atoms at intersections and line ends.
• Identify heteroatoms: one O atom is present, likely in a functional group like carbonyl or alcohol.
• Calculate hydrogens: each C needs 4 bonds; with bonds to other C and O accounted for, 8 H atoms fill remaining valences.
• Combine counts: yields C₄H₈O, matching option A.

Why A is correct:

• Skeletal formula depicts exactly 4 C, 8 H (implied), and 1 O, adhering to organic valence rules.

Why the others are wrong:

• B: Requires 5 C atoms, but structure has only 4.
• C: Requires 6 C atoms, exceeding the visible 4.
• D: Requires 7 C atoms, far more than shown.

Final answer: A