Identify the organism that is $NOT$ involved in commensalism.

Given below are two statements:
Statement $I$: Gause's competitive exclusion principle states that two closely related species competing for different resources cannot exist indefinitely.
Statement $II$: According to Gause's principle,during competition,the inferior will be eliminated. This may be true if resources are limiting.
In the light of the above statements,choose the correct answer from the options given below :

Which of the following examples does $NOT$ represent competition?

The number of individuals of a species in a particular ecosystem at a given time remains constant due to

Which of the following is an important morphological defense mechanism in plants against herbivores?

Explain competition in detail.