What & Why (06)

This will be a progressive exercise. When each question has been answered we will move on to the next.

1. Teams. Dealer East all vul.

A984
K932
J
A762

You are SOUTH.
The dealer East to your right opens 5D. What do you bid?

Do you a) PASS or b) DOUBLE

Then 2.
What do you lead and Why?