| A. | In both parasitism and commensalism, only one species benefits and the other species is harmed. |
| B. | Both species benefit in mutualism. |
| C. | Both species benefit in commensalism. |
| D. | In parasitism, only one species benefits and the other species is harmed |
| E. | In amensalism, one species is harmed and the other is unaffected. |
| 1. | A and D only | 2. | A and B only |
| 3. | B and E only | 4. | B, D and E only |