Which of the following is an aspect of a countercurrent exchange system? A. Active movement against a concentration gradient
B. Parallel movement induced by a concentration gradient
C. Passive movement induced by a concentration gradient
D. Random movement against a concentration gradient

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.