1started / just / i've / exercise / this. 2 already / we've / this / grammar / studied . 3 teacher / yet / arrived / the / hasn't . 4 test / the / started / just / has. 5 finished / i / this / yet / exercise / haven't. 6 had / already / we've / lunch .

1) I've just started this exercise
2) We've already studied this grammar
3) The teacher hasn't arrived yet
4) The test has just started
5) I haven't finished this exercise yet
6) We've already had lunch