What type of interaction exists between leguminous plants and $Rhizobium$ bacteria?

How can interspecific parasitism be represented?

Give scientific reasons: The members of a population do not breed with other populations.

Given below are two statements.
Statement $I$: Intraspecific competition occurs between organisms of the same population.
Statement $II$: Such interaction may be beneficial,harmful or neutral to the interacting individuals.
In the light of the above two statements,choose the correct option.

From the given options,identify the correct combination of population interactions that correspond to the symbols given here.

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