Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

The best explainer videos are realized by great background score. When was the last time you watched a silent movie? Never? Not for a while? A long while? Even if you remember watching one, it would still have had a background score, or you’ve accidentally pressed the mute button!

The importance of background music and sound effects for your explainer video, therefore, cannot be overstated. You may not need a full blown orchestra or classy jazz tones to create the mood, but whether going for a subtle effect, a professional demonstration or simply trying to attract customers, music is a must. Explainer videos have the emotional quotient working for them and music is just going to add more to make the viewers relate to the pain points you are highlighting in your video. Imagine if your favorite video game has no background music or sound effects to back the amazing graphics? Would you play it with the same feel and excitement? Nah! Same is the case with your explainer videos. They need to and should have apt sound effects to make them worth your viewer’s time.

While the focus of explainer videos production is more on passing the desired information and explaining technical and complex procedures easily, it doesn’t mean you’ll be distracting your viewers with the background music. The sound effects and music is not going to take the message away from your explainer, it’s just going to enhance it and turn it more watchable and share-able. Even if your video doesn’t require a background score, it must include some sound effects or else it would be not so good an experience for those who choose to watch it.

(source: https://www.b2w.tv/)

The word “it” in paragraph 3 refers to_____.

A. score

B. video

C. sound

D. background

Cho hình chữ nhật ABCD có AB = 8cm, BC = 15cm

a, Tính độ dài đoạn thẳng BD

b, Vẽ AH vuông góc với BD tại H. Tính độ dài đoạn thẳng AH

c, Đừng thẳng AH cắt BC và DC lần lượt tai I, K. Chứng minh:  A H 2 = H I . H K  

Cho Bx // Ny //Oz, O B x ^   =   130 °   v à   O N y ^   =   140 ° . Tính B O N ^ .