thế nào là âm phản xạ , tiếng vang ? Vật phản xạ âm tốt , vật phảm xạ âm kém?

giúp mik vs

D

1 giving => given

2 delivering => being delivered

3 keep => kept

4 doesn't => isn't

5 stealing => stolen

6 allowed => been allowed

7 open => opened

8 are => do

9 didn't invite => wasn't invited

10 find => found

a)\(\sqrt{\dfrac{10000}{\sqrt{400}}}\)+\(\sqrt{\left(3\right)^2}\).\(\sqrt{6^4}\)

b)\(\sqrt{1600}\):\(\sqrt{25}\)+\(\sqrt{49}\).\(\sqrt{16}\)-\(\sqrt{\left(-10\right)^2}\)

giup mik ai nhanh mik se tick cho nhe

1 D

2 B

3 D

4 B

5 A