[单选题]
Which of the following is/ +;m /ii0wivhc5-(yo ss4o ughare true for holozoic nfln .mh9vk/,h utrition?
I. Demonstrated by saprotrophs
II. Involves complete or partial ingestion
III. Food is digested internally
A. I and II only
B. II and III only
C. I and III only
D. I, II and III