Pasteur’s experiments and similar ones that followed, convinced most people that spontaneous generation of life did not happen because
(a) Pasteur was extremely meticulous
(b) Pasteur used very fine mesh screens to cover his flasks.
(c) Pasteur did not boil his flasks for a long time
(d) Pasteur’s swan- necked flasks ruled out the objection that spoiled air could have contaminated his experiments.

Hint: Louis Pasteur was an exemplary scientist of his time who invented the technique of pasteurization which is still used now to make pasteurized milk. His experiment to disprove spontaneous generation changed the perception of the origin of life.

Complete Step by Step Answer:
The theory of spontaneous generation states that living beings arose out of non- living things spontaneously.
This idea was proposed by Aristotle and was believed to be true for a long time because it supported the idea that God made humans from non- living things such as sand.
But this theory has been rejected ever since Pasteur’s swan neck experiment.

So, the correct option is 'Pasteur’s swan-necked flasks ruled out the objection that spoiled air could have contaminated his experiments'.

Additional information: Let us know the swan neck experiment in detail.
- Pasteur heated some soup and sterilized it and put it in a flask having a swan- shaped neck. The flask was also sterilized.
- The steam coming from the soup got deposited in the s- shaped neck of the flask and formed a plug there.
- This prevented contamination of the soup by the outside world.
- No matter how much time passed no living organisms were detected in the soup.
- Living organisms only appeared when the neck was broken i.e. contamination from outside.

Note: Louis Pasteur is a French scientist who is also known as the father of immunology.
The theory of spontaneous generation was also disproved by showing maggots didn't arise out from a dirty cloth unless there were maggot eggs present in it already. Now, the theory of abiogenesis which states living beings arose from non- living beings through slow evolutionary forces is accepted.