Which of the following is the correct structure of L-fructose?

Step 1: D-Fructose Configuration — In $\text{D-fructose}$, the configuration at the chiral centers (C3, C4, C5) is OH on the left, right, and right respectively.

Step 2: L-Isomer Relation — The $\text{L-isomer}$ is the mirror image of the $\text{D-isomer}$ at every chiral center.

Step 3: Determining L-Fructose — In $\text{L-fructose}$, the configurations are reversed: OH on the right (C3), left (C4), and left (C5). This corresponds to structure (c).

Key Point: The D/L configuration is determined by the orientation of the $-\ce{OH}$ group on the highest-numbered chiral carbon.