set out和set off的区别

a) set off 动身，出发，燃放(鞭炮等)，使……爆炸(发出响声)，引起(做某事)
We set off at dawn.
She usually sets off for school at 6:30.
“Stop thief!” cried John and set off after him.
People still set off fireworks in the countryside in Spring Festival.
If the TNT is shaken or roughly handed, it will be set off.
I accidentally pressed the button and set off the alarm clock.
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b) set out 动身，启程，出发，开始，着手，准备(做某事)

set out to do sth， set off doing sth，都是开始做某事