Đáp án + Giải thích bước giải:

1. Beginners of foreign language always meet difficulties at first

→ thì HTĐ: S(số nhiều) + V0 + ...

→ dấu hiệu: always

2. She is bilingual in Vietnamese and English 

→ bilingual (adj): nói 2 thứ tiếng

3. My father stopped smoking three years ago

→ thì QKĐ: S + V2/ed + ...

→ dấu hiệu: three years ago

4. Mr. Green didn't use to take his children to the circus last year

→ sau not + V0

→ use to + V0: đã từng

5. Although the internet has lots of benefits ,it isn't not only costly and time-consuming but also dangerous

→ Although + S + V, S + V...

=>

1. Beginners of foreign language always meet difficulties at first.

-> always (HTĐ, S Vs/es)

2. She is bilingual in Vietnamese and English.

-> bilingual: thông thạo 2 thứ tiếng

3. My father stopped smoking three years ago.

-> three years ago (QKĐ, S V2/ed)

4. Mr. Green didn't use to take his children to the circus last year.

-> used to V: đã từng/phủ định: didn't use to V

5. Although Internet has lots of benefits, it is not only costly but also very dangerous and time-consuming./Although Internet has lots of benefits, it is not only costly and time-consuming but also very dangerous.

-> although: mặc dù