Let's think step by step! Many _ can cause the immune system to not work properly.
Options:
- (A) fever
- (B) bacteria
- (C) radiation
- (D) fungi
- (E) A drug.
- (F) Allergies
- (G) cancers
- (H) Toxicity
The thinking starts now:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Immunodeficiency occurs when the immune system is not working properly. Many cancers can cause immunodeficiency. Many cancers can cause the immune system to not work properly. The final answer: (G).