exercise 6: write the affirmative,negative,or integrative in the past participle of these following sentences 1(+) I have finished my homework (-) (?) 2(+) (-) My ucle hasn't been to Singapore before (?) 3(+) (-) (?) Have they found their keys? 4(+) Jim has just played video games with his brother (-) (?) 5(+) (-) my grandmother hasn't viesited me since November (?) 6(+) (-) (?) Has your sister studied Medicine for 2 years? 7(+) It has been long since our last encouter (-) (?) 8(+) (-) We haven' graduated yet (?)