To address the problem of disproving spontaneous generation, which of the following options provides a key difference between the experiments of John Needham and Lazzaro Spallanzani?

Needham boiled the broth to kill any existing microorganisms, whereas Lazzaro Spallanzani did not boil the broth.

Spallanzani also boiled broth, but he boiled it for a shorter period than Needham.

Spallanzani also boiled broth, but he did not seal the flask.

Spallanzani boiled broth for a longer period and sealed the flasks more effectively, preventing contamination from the air.