Identify what cellulose is

Cellulose is a polysaccharide made up of many units of $\beta$-D-glucose joined by $\beta(1\to 4)$ glycosidic bonds.

Meaning of complete hydrolysis

Complete hydrolysis breaks all the glycosidic bonds in cellulose, converting the polymer into its monomer units.

Monomer obtained from cellulose

Since cellulose is composed of $\beta$-D-glucose units, complete hydrolysis gives D-glucose.

Check the options

• A: D-ribose — incorrect, ribose is a pentose sugar, not the monomer of cellulose.
• B: D-glucose — correct.
• C: L-glucose — incorrect, cellulose contains D-glucose units, not L-glucose.
• D: D-fructose — incorrect, fructose is not the monomer unit of cellulose.

Final answer

Therefore, complete hydrolysis of cellulose gives: $\boxed{\text{D-glucose}}$