1.There__once___be a big free in front of our classroom.once:曾经.
2.She ___introduced____her friend yesterday.introduce,及物动词.
3.The girl seemed to do these things___on purpose____yesterday.
on purpose:adv.故意.还有,deliberately(adv.)也是故意的意思
4.I'm very busy___now___and can't speak to you.结合语境.