Microscopic examination of a patient's sputum shows aseptate fungus. Which of the following is an aseptate fungus?

In biopsy specimens, Rhizopus is seen microscopically as nonseptate hyphae with broad, irregular walls and branches that form more or less at right angles. Cultures show colonies with spores contained within a sporangium. These organisms are transmitted by airborne asexual spores and invade tissues of patients with reduced host defenses. Patients with diabetic ketoacidosis, burns, or leukemia are paicularly susceptible. Ref: Levinson W. (2012). Chapter 50. Oppounistic Mycoses. In W. Levinson (Ed), Review of Medical Microbiology & Immunology, 12e.