If $'+'$ sign is assigned to beneficial interaction, $'-'$ sign to detrimental and $'O'$ sign to neutral interaction, then the population interaction represented by $'+'\, '-'$ refers to

Competition occurs when

Between which among the following, the relationship is not an example of commensalism?

Many parasites have evolved to be …$A$… in such a way that both host and the parasite tend to …$B$… that is, if the host evolves special mechanisms for rejecting or resisting the parasite, the parasite has to evolve mechanisms to …$C$… and neutralize them, in order to be successful with the same host species

Choose the correct option for $A , B$ and $C$

Give a suitable example for commensalism.