Option (a) is the correct answer because some scientists believe that life came from outside. Early Greek thinkers thought units of life called spores were transferred to different planets including earth. This transfer of spores was termed Panspermia.

Option (b) is not the correct answer because theory of spontaneous generation gave the idea for creation of life from dead and decaying matter.

Option (c) is not the correct answer because creation of life from chemicals was the basis for chemical evolution.

Option (d) is not the correct answer as formation of sperm in testes is known as spermatogenesis.