To complete the passage, let's analyze the context and select the best answers for each blank.

1. For blank (4), "__________, teenagers are pressured to study." The best option is:
- **A. social** (This implies that in modern society, teenagers feel social pressure to study.)

2. For blank (5), "Besides, they have to take extra lessons to keep up ____ their friends..." The best option is:
- **A. and** (This connects their need to keep up with their friends.)

3. For blank (6), "teenagers lose confidence in ____." The best option is:
- **B. self** (This indicates that teenagers lose confidence in themselves.)

4. For blank (7), "If they don't really understand, they may become angry or worried, sad or ____." The best option is:
- **B. frustrated** (This describes another emotional state teenagers might experience.)

5. For blank (8), "One of the ____ is that they cannot define their goals." The best option is:
- **C. pressures** (This emphasizes the pressure they feel about their goals.)

6. For blank (9), "In the end, ____ may become disillusioned because they set high standards..." The best option is:
- **B. Therefore** (This indicates a conclusion based on what has been stated.)

7. For blank (10), "____, they think that they are completely useless in doing anything." The best option is:
- **C. Moreover** (This adds to the argument about their feelings of uselessness.)

So the best answers would be:

4. A. social
5. A. and
6. B. self
7. B. frustrated
8. C. pressures
9. B. Therefore
10. C. Moreover