Here are the corrections for each question:

1. **Question 1**:
- The underlined part that needs correction is **(C)** "raise". The correct term should be "rise".
- Corrected sentence: "There was a gradual **rise** in the number of literate males and females in the Mekong Delta."

2. **Question 2**:
- The underlined part that needs correction is **(B)** "there is". Since the guide is reporting something told in the past, it should be "there was".
- Corrected sentence: "The guide told the tourists that **there was** a good restaurant specialising in seafood just round the corner from the movie theatre."

3. **Question 3**:
- The underlined part that needs correction is **(D)** "winters". The correct term is "winter".
- Corrected sentence: "Mary and her sister just bought two new **winter** coats at the clearance sale."

In summary:
1. **C**
2. **B**
3. **D**