Fungi are a distinct group of organisms that are classified separately from algae. One of the key characteristics that differentiate fungi from algae is the composition of their cell walls. The correct answer to this question is option 'D', which states that the cell wall in most fungi is made up of chitin.

Fungi have Chitin cell walls:

- Fungi have cell walls that are composed primarily of chitin, a complex polysaccharide made up of nitrogen-containing glucose molecules. Chitin provides the fungi with structural support and protection. This is in contrast to the cell walls of algae, which are primarily composed of cellulose.

Algae have Chlorophyll:

- One of the characteristics of algae is the presence of chlorophyll. Chlorophyll is a pigment that is responsible for the green color in plants and algae. It plays a crucial role in photosynthesis, the process by which plants and algae convert sunlight into energy. Fungi, on the other hand, do not contain chlorophyll and are unable to carry out photosynthesis.

Fungi store food as Glycogen:

- Another difference between fungi and algae is the form in which they store their reserve food. Algae store their reserve food in the form of starch, while fungi store it in the form of glycogen. Glycogen is a complex carbohydrate that serves as an energy storage molecule in fungi, similar to how starch functions in algae.

Fungi are not dependent on light:

- Unlike algae, which are photosynthetic and require light for their energy needs, fungi are heterotrophic organisms that obtain their nutrition by decomposing organic matter or by forming mutualistic associations with other organisms. Fungi can thrive in a wide range of environments, including dark places where light is not available.

In conclusion, the key characteristic that differentiates fungi from algae is the composition of their cell walls. Fungi have cell walls made up of chitin, while algae have cell walls primarily composed of cellulose. Additionally, fungi do not contain chlorophyll and store their reserve food as glycogen, while algae contain chlorophyll and store their reserve food as starch.