What type of secretion is observed in the salivary glands and the exocrine part of the pancreas in vertebrates?

The four sketches $(A, B, C$ and $D)$ given below represent four different types of animal tissues. Which one of these is correctly identified in the options given,along with its correct location and function?

Structurally,sweat glands are ....

An example of a merocrine gland is:

What is a characteristic feature of simple epithelium?

Which of the following junctions helps to stop substances from leaking across a tissue?