Which of the following is an ectoparasite?

In biological interactions,what does the interaction type $(+, 0)$ represent?

Match the following columns:

Column-$I$	Column-$II$
$P. +,+$	$I. \text{Mutualism}$
$Q. -,-$	$II. \text{Parasitism}$
$R. -,0$	$III. \text{Competition}$
$S. +,0$	$IV. \text{Amensalism}$
$T. +,-$	$V. \text{Commensalism}$
	$VI. \text{Predation}$

Niche overlap indicates

In a humid climate,the presence of spines in shrubs is primarily:

Choose the correct statements regarding population interactions between two species.
$A$. In both parasitism and commensalism, only one species benefits and the other species is harmed.
$B$. Both species benefit in mutualism.
$C$. Both species benefit in commensalism.
$D$. In parasitism, only one species benefits and the other species is harmed.
$E$. In amensalism, one species is harmed and the other is unaffected.