Sure, I'll help you with that. Here are the correct forms of the verbs and the indicators for each tense:

**Exercise 5: Put these verbs in the parentheses into the correct form.**

1. I (see) **have seen** her before. *(Present Perfect - dấu hiệu: before)*
2. I (see) **saw** her last year. *(Simple Past - dấu hiệu: last year)*
3. Tom (never be) **has never been** in Hanoi. *(Present Perfect - dấu hiệu: never)*
4. I (read) **have read** the novel written by Jack London several times before. *(Present Perfect - dấu hiệu: several times before)*
5. What (you, do) **did you do** yesterday? *(Simple Past - dấu hiệu: yesterday)*
6. (You, watch) **Did you watch** TV last night? *(Simple Past - dấu hiệu: last night)*
7. She (be) **was** born in 1980. *(Simple Past - dấu hiệu: in 1980)*
8. He (write) **has written** a book since last year. *(Present Perfect - dấu hiệu: since last year)*
9. Mr. Green (teach) **has taught** English in this school since he (graduate) **graduated** from the university in 1986. *(Present Perfect - dấu hiệu: since; Simple Past - dấu hiệu: in 1986)*
10. Linh (read) **has read** this book so far. *(Present Perfect - dấu hiệu: so far)*

**Exercise 6: Use the given words to write the full sentences.**

1. I/buy/new/bag/yesterday.
=> I **bought** a new bag yesterday. *(Simple Past - dấu hiệu: yesterday)*

2. They/not finish/homework/ yet.
=> They **have not finished** their homework yet. *(Present Perfect - dấu hiệu: yet)*

3. They/not watch/TV/ last night.
=> They **did not watch** TV last night. *(Simple Past - dấu hiệu: last night)*

I hope this helps! Let me know if you need any more assistance.