Which of the following plants produces a poisonous cardiac glycoside chemical?

Mild grazing of plants by herbivores:

Even a plant species,which makes its own food,cannot survive alone; it needs soil microbes to breakdown the $A$ matter in soil and return the $B$ nutrients for absorption. And then,how will the plant manage pollination without an animal agent? It is obvious that in nature,animals,plants and microbes cannot live in $C$ but interact in various ways to form a biological community. Choose the correct option for $A, B$ and $C$.

What does the following figure represent?

Match the following symbols with their respective population interactions:

$A. +/+$	$I. \text{Predation}$
$B. -/-$	$II. \text{Ammensalism}$
$C. +/-$	$III. \text{Competition}$
$D. -/0$	$IV. \text{Mutualism}$

Select the correct match.

Column $I$ $\&$ $II$	Column $III$
$a. (+, -)$	$P. \text{Amensalism}$
$b. (-, -)$	$Q. \text{Commensalism}$
$c. (-, 0)$	$R. \text{Predation}$
$d. (+, 0)$	$S. \text{Competition}$