You must think hard before bursting these bubbles. You can only burst clusters of bubbles of the same colour and not single bubbles. 

The more bubbles you have in a cluster the higher your score will be. You should also consider how gravity will affect the bubbles that are left. 

Click once on the bubbles to see the score you'd get from bursting them and then click again to actually burst them. 

Try and score more than 120.