The first term and the common ratio of the G.P. 3, $\dfrac{3}{2}, \dfrac{3}{4}$, ………. are respectively :

1. 3 and 2

2. 3 and $\dfrac{1}{2}$

3. 3 and $\dfrac{3}{2}$

4. $\dfrac{3}{2}$ and $\dfrac{1}{2}$

In the given G.P.,

a = 3

r = $\dfrac{\dfrac{3}{2}}{3} = \dfrac{3}{2} \times \dfrac{1}{3} = \dfrac{1}{2}$.

Hence, option 2 is the correct option.