1) Lan are not in the classroom. She is outside.

are ---> is

2) Ngoc have a pet. It is a bird.

have ---> has

3) My friends doesn't play sports.

doesn't ---> don't

4) We likes cartoons but we don't like flims.

likes ---> like

5) He loves reading fairy tails.

tails ---> tail

6) Does you do your homework after school?

Does ---> Do

7) Is Ba and Nam from Viet Nam?

Is ---> Are

8) How often does Nga goes to the park?

goes ---> go

9) Do Mai and Ha play badminton? ----- No, they do.

do ---> don't

10) His family often have a picnic when he has free time

have ---> has

11) He never is late for school.

never is ---> is never

12) Does your mother work near your house? ----- Yes, she do.

 do ---> does 

Hai điện tích có độ lớn bằng nhau được đặt trong không khí cách nhau 12cm. Lực tương tác giữa hai điện tích đó bằng F. Đặt hai điện tích đó trong dầu và đưa chúng cách nhau 8cm thì lực tương tác giữa chúng vẫn bằng F. Tính hằng số điện môi của dầu

A. 1,5.

B. 2,25.

C. 3.

D. 4,5.