• Cell Wall Composition of Oomycota: Oomycetes (such as Phytophthora, Pythium, and downy mildews) belong to the kingdom Stramenopila (Chromista) rather than true fungi (Eumycota). Their cell wall is predominantly composed of cellulose ($eta$-1,4-glucan) and $eta$-1,3- and $eta$-1,6-glucans, with hydroxyproline-rich glycoproteins.
• Distinction from True Fungi: True fungi (Ascomycota, Basidiomycota, Zygomycota) possess cell walls containing chitin ($eta$-1,4-linked $N$-acetylglucosamine polymer). Oomycetes completely lack chitin or contain only minute trace amounts.
• Conclusion: The cell wall of oomycetes is rich in cellulose (Option 2).

Correct option: (2) Cellulose