Here are the corrections for the underlined parts:

**33.** The country was significantly changed since we came here in 2007.
**Correction:** "significantly changed" should be "significantly changed since".
**Answer: A**

**34.** Like her brother, Jane is very interested in Mathematics and their applications.
**Correction:** "their applications" should be "its applications".
**Answer: D**

**35.** I never read such romantic story this before I have like.
**Correction:** The correct order should be "I have never read such a romantic story before."
**Answer:** Rearrangement needed.

**36.** Alex doesn't know how he can get to the Thu Le Zoo. (TO)
**Correction:** "Alex doesn't know how to get to the Thu Le Zoo."

**37.** Mrs. Mai becomes older, she feels forgetful. (THE OLDER)
**Correction:** "The older Mrs. Mai becomes, the more forgetful she feels."

**38.** If you don't work harder, you will not pass the final exam. (UNLESS)
**Correction:** "Unless you work harder, you will not pass the final exam."

**39.** Lan Anh often looks after her younger brother after school. (TAKE)
**Correction:** "Lan Anh often takes care of her younger brother after school."

Feel free to ask if you need any further clarification!