I / have / toothache / so / I / have to / see / dentist.
A. I have a toothache so I have to see dentist.
B. I have toothache so I have to see dentist.
C. I have a toothache, so I have to see the dentist.
D. I have toothaches so I have to see the dentists.
Đáp án: C
Dịch nghĩa: Tôi bị đau răng nên tôi phải đến nha sĩ.