您不能成为献血者。

You can't be a blood donor.

You cannot be a blood donor.

Source: Tatoeba

Sentence Composition

1 您 nín you (courteous, as opposed to informal 你 nǐ)
2 不能 bùnéng
  1. cannot
  2. must not
  3. should not
3 成为 chéngwéi to become; to turn into
4 献血者 xiànxuèzhě blood donor