When upgrading Check Point products in a distributed environment, in which order should you upgrade these components?

When upgrading Check Point products in a distributed environment, in which order should you upgrade these components?

1 GUI Client

2 Security Management Server

3 Security Gateway

A.
3, 2, 1

B.
1, 2, 3

C.
3, 1, 2

D.
2, 3, 1