If G.R.I and I denote capacity, resistance, inductance and electric current respectively, the quantities having the same dimensions of time are : $(1)CR ,\; (2)\;\large\frac{L}{R},\;(3)\;\sqrt {LC}, \;(4)\;LI^2$

Question

(a) (1) and (2) only 

(b) (1) and (3) only

(c) (1) and (4) only 

(d) (1),(2) and (3) only