The correct option is D Effects of environment
Lamarck strongly supported the fact that if an organism is acquiring any characters, its surrounding environment is solely responsible for this change.
According to Lamarck’s theory of use and disuse, the organ which is used continuously will develop whereas the organ which is not used will either degenerate or remain the same.
Lamarck did not differentiate between changes in the somatic and germplasm of the body, in their role in inheritance. He also did not observe the importance of pre-existing variations in the populations for evolution, instead proposed that variations arise due to an internal vital force guided by the environmental changes.