How do you mark the crown thingy on a answer???

Idon’t know the answer and i’ve been stuck on it for a while now skskskskks

18. which statement about cancer is true?

What mistake did john needham make that caused him to conclude that spontaneous generation for microorganisms occurred? a. he re-contaminated his boiled broth solutions. b. he destroyed the vital force in the solutions. c. he did not boil his broth solutions, only warmed them. d. he failed to seal his flasks of boiled broth. e. he allowed his assistant to conduct the experiment which he did not monitor closely.