Which of the following acids is called 'the king of chemicals'?

Which of the following substances enters our body when a red ant bites us?

$A$ substance $X$, which is an oxide of a group $2$ element, is used intensively in the cement industry. This element is present in bones also. On treatment with water, it forms a solution which turns red litmus blue. Identify $X$ and write the chemical reactions involved.

Which among the following is not a base?

The Bronsted-Lowry acid-base theory was based on which of the following?

State whether the following statement is true or false:
Acids produce $H_{3}O^{+}$ or $H^{+}(aq)$ ions in water.