touch off
phrasal verbtouch something  off 
- to make something begin, especially a difficult or violent situation触发,引发,引起(困难或暴力的局面) - The blaze was touched off by lightning.这场大火是由闪电引起的。 
- Her comments touched off a wave of protests.她的评论引发了一波抗议。 
 
- The blaze was touched off by lightning.