D is disturbed, and ultimately all the pendulums start oscillating. Match the following

`{:("1. Oscillations of A","(a) free oscillation"),("2. Oscillations of B","(b) forced oscillation"),("3. Oscillations of C","(c) Resosnant oscillation"),("4. Oscillations of D",):}`

Explanation

`because` D is disturbed initially so D will execute free oscillation and all other forced oscillation. But the length of B & D are equal so their frequencies are same therefore B will be in resonance with D.
`1 rarr (b) " "2 rarr (b), (c)" "3 rarr (b)" "4 rarr (a)`