1. My sister is very seriously and hard-working in her...

=> A. seriously -> serious (tobe + adj)

2. Ride a  bike at the weekend is my best friend's hobby.

=> A. ride -> riding (Khi động từ làm chủ ngữ phải thêm -ing)

3. She is very cared, so she always helps her mother do the housework.

=> B. cared -> careful

4. My friend has a short brown hair and an oval face.

=> B. a (thừa; vì hair là danh từ ko đếm được nên ko dùng a)

5. Because Nga is very keen on the school's singing competition, she is taking part on it tomorrow.

=> D. on -> in (take part in...: tham gia...)

6. I have an important maths exam tomorrow afternoon, so I do a lot of maths exercises this evening.

=> C. do -> did (this evening dùng thì QKĐ)

7. We have a lot of assignments to do. Therefore, we are going to the cinema with you tonight. 

=> therefore -> however 

8. I have new pencil, a pencil sharpener, and a pencil case.

=> A. new pencil -> a new pencil (Thiếu mạo từ)

9. The painting competition will start at his school on the 17th of October.

=> at -> in (Dùng sai giới từ)

10. She usually plays the piano every Monday evening, but today she watch cartoons with her younger sister.

=> watch -> watches (Dùng thì HTĐ: She + V-s, es)

11. There are a table, four chairs, two pictures and a vase in the living room.

=> A. are -> is (a table là số ít)

12. There aren't a lot of posters in the wall in his bedroom.

=> C. in -> on

13. My dog has a long tail, big eyes, and a yellow fur.

=> a (thứ hai)-> bỏ đi vì fur = lông ko đếm được

14. She has a birthday party with a big birthday cake and a lot of candles at home.

=> A. has -> is having