Candida albicans is the most common cause of candidiasis because it is a normal commensal organism of the human mucosa that can become pathogenic under conditions of immunosuppression, antibiotic use, or disruption of normal flora. It exhibits the ability to switch between yeast and hyphal forms, facilitating tissue invasion and evasion of the host immune response. This polymorphism is key to its virulence, making it the predominant species responsible for both superficial and systemic candidiasis. Other fungi listed do not commonly cause candidiasis.

Reference: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, J.E. Bennett et al., 9th Edition.