All the elements in a group (family) have a common valency. For example, all the elements of the carbon family (carbon, silicon, germanium, tin and lead ) have common valency four. However, some of these elements can also have valency two. Which of the following can have valency two?

The major component used in preparation of different types of glasses is

The main constituent of vinegar is

Statement I :
Water (H₂O) is more polar than Hydrogen Sulphide (H₂S).

Statement II :
Oxygen is more electronegative than Sulphur.

When the winds blow from all sides to the central low in an anticlockwise direction, then this phenomenon is known as

The acid in gastric juice is