Khoảng cách giữa hai điểm gần nhau nhất trên cùng một phương truyền sóng dao động ngược pha nhau là: \(\dfrac{\lambda}{2}=0,85\left(m\right)\)

\(\Rightarrow\lambda=0,85.2=1,7\left(m\right)\)

Tần số của âm là:

 \(\lambda=\dfrac{v}{f}\\ \Leftrightarrow f=\dfrac{v}{\lambda}=\dfrac{340}{1,7}=200\left(Hz\right)\)

=> Chọn đáp án B

Daniel signs up for a clean-up campaign so that he can join it

IV. Give advice with “should” or “shouldn’t”, using the words in brackets.

Example: I feel very tired. (take/short rest) → I should take a short rest.

1. Minh’s room is very dirty. (clean / room/ every day)

→ He should .....clean his room every day..................................................................................................................

2. It’s raining heavily outside. (go out)

→ We shouldn’t .....go out............................................................................................................

3. We’ll have an English test tomorrow. (learn/ lessons/carefully)

→ We .......should learn our lessons carefully.........................................................................................................................

4. Hoa feels sleepy. (stay up late)

→ Hoa ....shouldn't stay up late...........................................................................................................................

5. We are in the library. (talk/ too loudly)

→ We .....shouldn't talk too loudly............................................................................................................................

6.  Phong has a sore throat. (drink/warm water/ go/the doctor)

→ He ......should drink warm water and go to the doctor...........................................................................................................................

VII. Rewrite these statements as reported speech with tense changes.
1. ‘I’m reading a Science book.”
She told me_that she was reading a Science book______________________________________________________

Lùi thì: Hiện tại tiếp diễn (am/is/are + Ving) => quá khứ tiếp diễn (was/were + Ving)

Đổi ngôi: I => she

2. “The 8.30 flight to Da Nang will be delayed for 2 hours.”
They announced that __the 8.30 flight to Da Nang would be delayed for 2 hours_______________________________________________

Lùi thì: will + be+ V3/ed => would + be + V3/ed

3. “We have applied a new production Chain.”
The CEO of Volkswagen said that___they had applied a new production Chain____________________________________

Lùi thì: Hiện tại hoàn thành (has/ have + V3/ed) => Quá khứ hoàn thành (had + V3/ed)

Đổi ngôi: we => they

4. “The invention of light bulb is very important.”
My teacher said that__the invention of light bulb was very important________________________________________________

Lùi thì: Hiện tại đơn => Quá khứ đơn

5. “My engineers can assemble 5 car engines a week.”
The director said that__his engineers could assemble 5 car engines a week_______________________________________________

Lùi thì: can => could

Đổi ngôi: my => his

6. “I hope you will build the airport with lowest cost.”
The Prime Minister told foreign investors that__he hoped they would build the airport with lowest cost___________________________

Lùi thì: Hiện tại đơn (hope) => Quá khứ đơn (hoped)

will + V => would + V

Đổi ngôi: I => he

you => they

7. “We plan to make the City a safer place for everyone.”
The local MP said that____they planned to make the City a safer place for everyone____________________________________________

Lùi thì: Hiện tại đơn (plan) => Quá khứ đơn (planned)

Đổi ngôi: we => they

8. “My family lived in Boston for five years.”
Carol said that____his family had lived in Boston for 5 years__________________________________________________

Lùi thì: Quá khứ đơn (V2/ed) => Quá khứ hoàn thành (had + V3/ed)

Đổi ngôi: my => his

9. “We may cut down on fossil fuels.”
They said that__they might cut down on fossil fuels_____________________________________________________

Lùi thì: may => might

Đổi ngôi: we => they

10. “James Watt invented the steam engine in 1769.”
Ms. Elena told us that_James Watt had invented the steam engine in 1769________________________________________________

Lùi thì: Quá khứ đơn => Quá khứ hoàn thành

1 I wish I didn't have to study hard

2 I wish we hadn't had a lot of homework yesterday

3 I wish it weren't raining heavily

4 I wish it hadn't been cold last night

5 I wish they didn't work slowly

6 I wish she joined the trip

7 I wish I were good at English

8 I wish I had a computer

9 I wish today were a holiday

10 I wish I could sing that song

11 I wish they would come here again

12 I wish these students didn't talk too much in class

(Đề câu này có chữ " talks " sai ngữ pháp nha => students số nhiều thì chia động từ thành talk)

13 I wish I could play basketball

14 I wish it didn't rain today

15 I wish I were rich

was not

a. is opened

b. was being pulled down

c. had been cleaned

d. Has the rubbish been collected

Chọn B (phát âm /d/, các từ còn lại /t/)

(Tham khảo cách đọc trên mạng nhee, cũm dễ học lắm bạn, ngta có chỉ mẹo nx nè)

16 will be opened next Monday

17 is spent on advertising everyday

18 câu này bị sai nè bạn, trong đề đâu có chữ " the victims " thì sao viết lại được :vv

=> The reports are being written on environment now

19 is going to be bought next year

20 is being sung now

21 machine was mended by Mr. Dryden

22 is too small for us to live in

23 arrived while we were having lunch

24 I found that film boring

or I think that film was boring