C

D

PUT THE CORRECT VERB FORM 
1. He usually.........jogging............ (jog) in the morning.
2. My brother......is watching............. (watch) TV at the moment.
3. Hoa.......doesn't go..................... (not go) fishing in the winter.
4. Her sister..........is skipping................. (skip) now.
5. There..............isn't.............. (not be) any water in the bottle.
6. At the moment, the children....are playing................. (play) soccer in the garden.
7. Alice (not take).......doesn't take..........the bus to school every day. She usually (walk)..walks........ instead.
8. She (go)...goes........... to school everyday.
9. He (not have).....doesn't have................. any car.
10. It often (rain)..rains............ in summer. It (rain)..........is raining............ now.
11. What ……do……..you often (do)..do............. in the morning?
12. Mai (go) ..goes........to school in the morning. She (not go)..doesn't go...to school in the afternoon.
13. They (play) ...are playing........volleyball in the school yard now.
14. How often ....does...he (go) .go......swimming? twice a week.
15. Nga (brush)______brushes_____ her teeth after dinners.

ý??

ta có công thức chung: \(S^{IV}_x\)\(O^{II}_y\)(x,y thuộc N*)

theo qui tắc hóa trị:

IV.x=II.y

-> x/y=II/IV=1/2

thay x=1 y=2 vào CTC:\(SO_2\)

S\(O_2\)

x=9

trung bình mỗi đợt đội thủy lợi sửa đc là:

(37+49):2=43m

B

my school is in front of a big stadium