Spanish: Accent Marks On Question Words In A Statement
Should the following question words have accent marks in a statement like "I don't know WHO bought the horse." or do they drop their accents?

Yo no se... (I don't know...)

1. quién / quien compró el caballo. = who bought the horse.

2. qué / que ella compró. = what she bought.

3. dónde / donde ella compró el caballo. = where she bought the horse.

4. cuándo / cuando ella compró el caballo. = when she bought the horse.

5. por qué / por que ella compró el caballo. = why she bought the horse.

6. cómo / como ella compró el caballo. = how she bought the horse.

7. cuántos / cuantos caballos ella compró. = how many horses she bought.

Question

Spanish: Accent Marks On Question Words In A Statement
Should the following question words have accent marks in a statement like "I don't know WHO bought the horse." or do they drop their accents?

Yo no se... (I don't know...)

1. quién / quien compró el caballo. = who bought the horse.

2. qué / que ella compró. = what she bought.

3. dónde / donde ella compró el caballo. = where she bought the horse.

4. cuándo / cuando ella compró el caballo. = when she bought the horse.

5. por qué / por que ella compró el caballo. = why she bought the horse.

6. cómo / como ella compró el caballo. = how she bought the horse.

7. cuántos / cuantos caballos ella compró. = how many horses she bought.

Answer

All of them must have accent mark. Use this tip, if you can transform sentence in a question, you must use accent marks.

Regards

Answer

Oh this is a difficult one even for me that i speak spanish natively.
You should use accent marks in those words specifically but only if they are inside a question ¿?.
If they are not you don't have to use it.