High density of elephants in a specific area is a result of which of the following?

Which of the following is $NOT$ a characteristic of a parasite's effect on its host?

Which of the following is a correct pair?

Death of the host shall be disastrous to:

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Abingdon tortoise in Galapagos islands became extinct within a decade after goats were introduced.
Reason $R$: Goats were more efficient at browsing than Abingdon tortoise.
In the light of the above statements, choose the most appropriate answer from the options given below:

Which type of interrelation is observed in species $A$ $(+)$ and species $B$ $(-)$?