Identify cells $P$ and $Q$ in the given areolar connective tissue diagram.

Which cells secrete collagen fibers?

How many major types of connective tissues are there?

In organisms, where are sulfates primarily found?

Mast cell is a cell of $A$ of vertebrate animals. Mast cells mediate inflammatory responses such as $B$. Mast cells store a number of different chemical mediators including $C$ and $D$. Here $A$ to $D$ refers to:

Select the correct pair.