what needs to be shown while traveling outside USA??

[aab.tx]

what needs to be shown to officer while traveling outside USA??
is it passport or GC?
is it mandatory to keep passport when I have GC traveling to USA & from USA.?

[newacct]

This is very unclear. What do you mean by "officer while traveling outside USA"? Are you asking about when you are leaving or re-entering the US? When leaving the US, you do not see any "officer", because the US has no exit checks (no matter if you leave by land, sea, or air). When entering the US, as far as the government is concerned, a valid green card is enough by itself. The airline will usually also require you to have a passport.