The $pH$ of blood in the human body is maintained by $CO_2$ and $H_2CO_3$. What is this process called?

In which of the following combinations is buffer action expected?
$(a)$ $NH_4OH + NH_4Cl$
$(b)$ $HCl + NaCl$
$(c)$ $NH_4OH + HCl$ in $2:1$ mole ratio
Select the correct answer using the code given below.

The addition of small amounts of either acid or base to a buffer solution causes only small changes in $pH$ because the buffer solution

Which buffer solution out of the following will have $pH > 7$?

$A$ solution of $H_3BO_3$ and borax is known as:

Which of the following solutions can act as a buffer?