Which of the following interactions is represented by the $(-, +)$ relationship between species $A$ and species $B$ respectively?

Why do parasites exhibit parasitism?

Which of the following is an example of competitive interaction?

Observe the set of $4$ figures $A$,$B$,$C$ and $D$ and answer the following questions:
$(i)$ Which one of the figures shows mutualism?
$(ii)$ What kind of association is shown in $D$?
$(iii)$ Name the organisms and the association in $C$.
$(iv)$ What role is the insect performing in $B$?

Pollinator mutualism are special interactions involving ...$A$...,which receive food or a place to lay eggs and ...$B$...,which receive pollen from others of their kind. Choose the correct option for $A$ and $B$.

Whose field experiment showed that on the rocky sea coast, the larger and competitively superior barnacle excludes the smaller barnacle?