A saturated acyclic hydrocarbon with the molecular formula C_7 H_...

The given molecular formula is $\mathrm{C}_7 \mathrm{H}_{16}$, which represents a saturated acyclic hydrocarbon (alkane).

Analyzing the given options based on the types of carbon atoms present:

For 2,2-dimethylpentane, the structure is $\mathrm{CH}_3-\mathrm{C}(\mathrm{CH}_3)_2-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{CH}_3$. It contains one quaternary carbon (C2) and zero tertiary carbons.

For 3-ethylpentane, the structure is $\mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}(\mathrm{C}_2\mathrm{H}_5)-\mathrm{CH}_2-\mathrm{CH}_3$. It contains one tertiary carbon (C3) and zero quaternary carbons.

For 2,3-dimethylpentane, the structure is $\mathrm{CH}_3-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}_2-\mathrm{CH}_3$. It contains two tertiary carbons (C2 and C3) and zero quaternary carbons.

For 2,2,3-trimethylbutane, the structure is $\mathrm{CH}_3-\mathrm{C}(\mathrm{CH}_3)_2-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}_3$. The carbon atom at position 2 is bonded to four other carbons, making it a quaternary carbon. The carbon atom at position 3 is bonded to three other carbons, making it a tertiary carbon. It has exactly one tertiary and one quaternary carbon atom.

Thus, 2,2,3-trimethylbutane satisfies all the given conditions.

Answer: 2,2,3-trimethylbutane