Question: In between two rational numbers there is/are :

1. Only irrational number
2. Exactly one rational number
3. Infinitely many rational numbers
4. Many irrational numbers

Solution :
The correct option is 1.  Infinitely many rational numbers
Recall that to find a rational number between r and s, you can add
$\mathrm{r}$ and $\mathrm{s}$ and divide the sum by 2 , that is $\frac{\mathrm{r}+\mathrm{s}}{2}$ lies between $\mathrm{r}$ and $\mathrm{s}$.
For example, $\frac{5}{2}$ is a number between 2 and 3
We can proceed in this manner to find many more rational numbers between 2 and 3.
Hence, we can conclude that there are infinitely many rational numbers between any two given rational numbers.