Which of the statements about Protoctista are correct?

1. A eukaryote that is not a fungus, plant or animal is a protoctist.

2. An organism with cellulose cell walls and chloroplasts may be a protoctist.

3. An organism existing as a group of similar cells may be a protoctist.

4. A single-celled heterotrophic eukaryote is a protoctist.

A. 1, 2, 3 and 4

B. 1, 2 and 4

C. 2 and 3

D. 3 and 4 only