Believers of spontaneous generation believed that life originated only spontaneously. Let's understand this statement in detail.

Explanation:
Spontaneous generation is the theory that proposed that living organisms could arise from non-living matter under certain conditions. This theory was widely accepted for many centuries, until it was disproven by Louis Pasteur in the mid-19th century.

a) Life originated from other similar organisms or spontaneously:
According to the theory of spontaneous generation, life could arise either from other similar organisms or spontaneously from non-living matter. However, this is not the correct answer as the believers of spontaneous generation did not consider the possibility of life originating from other similar organisms.

b) Life originated only spontaneously:
This is the correct answer. The believers of spontaneous generation argued that life could only originate spontaneously from non-living matter. They believed that under certain conditions, such as the presence of air, moisture, and organic material, life could arise spontaneously.

c) Life originated from similar organisms:
This is not the correct answer. The believers of spontaneous generation did not consider the possibility of life originating from similar organisms. They believed that life could only arise from non-living matter.

d) Life originated from air:
While air was considered to be one of the necessary conditions for spontaneous generation, it was not believed to be the source of life. The believers of spontaneous generation thought that life could originate from the combination of non-living matter, air, and other environmental factors.

In conclusion, the correct answer is option 'B' - the believers of spontaneous generation believed that life originated only spontaneously from non-living matter under certain conditions. However, it's important to note that this theory has been disproven by scientific experiments and observations, and the modern understanding of life's origin is based on the principles of biogenesis, which states that life only arises from pre-existing life.

Spontaneous generation or anomalous generation is an obsolete body of thought on the ordinary formation of living organisms without descent from similar organisms. Typically, the idea was that certain forms such as fleas could arise from inanimate matter such as dust or that maggots could arise from dead flesh. A variant idea was that of equivocal generation, in which species such as tapeworms arose from unrelated living organisms, now understood to be their hosts. Doctrines supporting such processes of generation held that these processes are commonplace and regular. The doctrine of spontaneous generation was coherently synthesized by Aristotle, who compiled and expanded the work of prior natural philosophers and the various ancient explanations of the appearance of organisms, it held sway for two millennia. So, believers of spontaneous generation theory believed that life originated only spontaneously and not originated from similar organisms, from air and  from other similar organism or spontaneously