$Ex1:$
$1.C$
$2.A$
$3.D$
$4.D$
$Ex2:$
$1.D$
$2.D$
$3.B$
$4.D$
$5.C$
$6.B$
$7.C$
$8.B$
$Ex3:$
$1. visit$
$2. walk$
$3. go$
$4. is, doing$
$5. are$
$6. is, watching$
$7. playing$
$8. do$
$Ex4:$
$1$. My school has 620 students
$2$. Bao often go to school on foot
$3$. Nam is shorter than hoang
$4$. Why don't we play badminton ?
$100$% $sure$
$Chúc,bạn,học,tốt,điểm,A+$