Mark the letter A, B, C, or D to indicate the underlined part that needs correction in each of the following sentences.

1. The teacher explained (A) of her students (B) the importance (C) of preserving (D) cultural identity.

2. Don't (A) forget to turn (B) out all lights (C) when the rooms are not (D) in use.

3. I (A) was finding an interesting biography (B) while I was looking (C) around the (D) bookshop.

4. When I (A) was arriving at my grandparents' house, they (B) were watching a programme about (C) the customs (D) of ethnic minorities in Viet Nam. 

5. As the second longest river in (A) the world, (B) an Amazon flows through several countries (C) in South America before emptying into (D) the Atlantic Ocean.

6. When my father studied in (A) the UK, he also learnt to play (B) a guitar and (C) performed in (D) a band.

7. After graduating (A) from university, my brother applied (B) to more than five jobs before he was invited (C) for his first job (D) interview.

8. My brother dropped (A) out of school (B) at 15, (C) that made it harder (D) for him to find a job.