II.

1.Unless the flood had risen higher, the crops would not have been ruined.
2.Unless you had sneezed, he would not have known that we were there.
3.Unless she did her hair differently, she would not look quite nice.
4.Unless john had played for our football team, we would have lost the game.
5.Unless I won a big prize in lottery, I wouldn't give up my job.
6.Unless you are carefully, you will cut yourself with that knife.
7.Unless you like this one, I'll bring you another.
8.Unless I have a quiet room, I'll not be able to do any work.
9.Unless she hurries, she will be late.
10.Unless we had more rain, our  croups wouldn't be better.

16.save
17.stopped
18.would (you) do
19.didn't hurry
20.had tried
21.wouldn't run
22.will promise
23.had permitted
24.would spend
25.will accept
 

6.traditional
7.fireworks
8.decorate
9.costumes
10.parade

VII.
35. try on
36. large
37. jeans changing room
38. Sales assistant
39. customer
40. sweater
41. medium
VIII.
43. try
44. seafood
45. fish
46. Fry
47. noodles
48. pork
49. sauce
50. herbs

29. We often go to the library to read books and study.
30. I think you should participate in the talent show because you can sing very well.
31. We are usually at home on Sundays.
32. My mother sometimes helps me with my homework.
33. When is there a festivial in your city?

:D

a, Đúng
Giải thích:
\(T=\dfrac{1}{f}=\dfrac{1}{20}=0,05s\)
b, Sai
Giải thích:
Vì M là thuộc cực đại mà giữa M và đường trung trực của S1S2 có 3 cực đại khác nên M thuộc cực đại bậc 4.
c, Đúng
Giải thích:
M là cực đại bậc 4 nên ta có:
\(MS_1-MS_2=4\lambda\)
\(\Rightarrow34-22=4\lambda\)
\(\Rightarrow\lambda=3cm\)
d, Sai
Giải thích:
Ta có: \(v=\dfrac{\lambda}{T}=\dfrac{3}{0,05}=60\)cm/s

\(\overrightarrow{F_x}\perp\overrightarrow{F_y}\) \(\Rightarrow cos30^o=\dfrac{F_x}{F}\)\(\Rightarrow F_x=F.cos30^o=100.cos30^o=50\sqrt{3}\left(N\right)\)
Ta co': \(F_y=\sqrt{F^2-F_y^2}=\sqrt{100^2-\left(50\sqrt{3}\right)^2}=50\left(N\right)\) (theo đinh lý pytago)
Vậy \(F_x=50\sqrt{3}N,F_y=50N\)