Cells that perform similar functions group together to form what?

Match the following columns:

Column-$I$	Column-$II$
$P$. Tight junctions	$I$. Stop substances from leaking across a tissue
$Q$. Adhering junctions	$II$. Perform cementing to keep neighbouring cells together
$R$. Gap junctions	$III$. Facilitate the cells to communicate with each other by connecting the cytoplasm of adjoining cells,for rapid transfer of ions,small molecules and sometimes big molecules

The nature of the mammary gland is:

The inner lining of the vagina is composed of which type of epithelium?

Sweat glands are classified as:

Which of the following statements is/are correct regarding epithelial tissue?
$a$ - Cells are compactly packed.
$b$ - Cells have little intercellular matrix.
$c$ - It can be single or multi-layered.