Trance — At the beginning of combat on your turn, mill two cards. Terra gains flying until end of turn. Whenever Terra deals combat damage to a player, you may pay . When you do, return target creature card with power 3 or less from your graveyard to the battlefield tapped.
原文You don't choose a target for Terra's last ability at the time it triggers. Rather, a second "reflexive" ability triggers when you pay 2 this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.