My wife is planning to go abroad (South Asia) for a week and will be coming back to USA alone. In the past whenever she traveled outside USA, I always accompanied her on her way back. We use to retain our original I-94s which helped us not to be scrutinized upon entry. Since she will be traveling alone this time, what documents (in addition to her I-94 and the copy of my I-94) should she carry to avoid any trouble while re-entering in US.