When are the 'lubb' and dubb' sounds produced by heart?

Lub sound produced by heart is caused by

Lub sound produced by heart is caused by

Lub sound produced by heart is caused by

Describe the sequence of events which occur in the cardiac cycle in humans. Where and how are the sounds lubb and dubb produced in the heart during this cycle ?

What is the reason for the Lubb- dubb sounds of the heart?

The second heart sound is produced

The second heart sound is produced