You never see any cattle or goat browsing on $Calotropis$ due to

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

Cattle or goats are never seen browsing on $Calotropis$ growing in abandoned fields because of the presence of:

The orchid $Ophrys$ employs 'sexual deceit' to get pollinated by a species of bee. One petal of its flower bears an uncanny resemblance to the female of the bee in size,colour,and markings. The male bee perceives it as the female and attempts to copulate with the flower. During this process,pollen grains are dusted on the male bee's body. What is this phenomenon called?

Commensalism can be represented as :

Which of the following is an example of a parasite living on another parasite?