原文Speed's last ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered or otherwise leaves the stack without resolving.
原文You don't choose a target for Speed's last ability at the time it triggers. Rather, a second "reflexive" ability triggers when you pay 1 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.