Which experimental technique was employed by John Needham to back up his theory of spontaneous generation?

• A. Boiling the broth, letting it cool for some time, and then sealing it.
• B. Keeping broth in an open container at room temperature.
• C. Filtering the air before the broth comes into contact with it.
• D. Heating up the soup and tightly sealing it.

Answer: (A)