The correct answer is A. CnH2n + 2.
Alkanes are saturated hydrocarbons, in which a single bond is found between two carbon atoms. The general formula for alkanes is CnH2n + 2, where n is the number of carbon atoms in the molecule.
Option B, CnHn + 1, is the general formula for alkenes, which are unsaturated hydrocarbons that have one or more double bonds between carbon atoms.
Option C, CnH2n – 1, is the general formula for alkynes, which are unsaturated hydrocarbons that have one or more triple bonds between carbon atoms.
Option D, CnH2n + 1, is the general formula for cycloalkanes, which are saturated hydrocarbons that have a ring structure.