This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oral Cavity, Subject name: Surgery
50 year tobacco chewer comes with chief complaints of a mass in the oral cavity of 1.5 cm with a single lymph node size <3 cm on ipsilateral neck. TNM stage is....... 
Select and explain. 
A. T1 N3, B. T3 N1, C. T2 N2, D. T1 N1
D: T1 N1
Answer: D: T1 N1 
Explanation: Ans. (d) T1 N1Ref: Bailey and Love Page 709Staging of Oral cavity Cancer:* T1 - <2cm* T2- 2-4cm* T3 - 4-6cm* T4 - adjacent structure involvement* N1-Ipsilateral single node <3cm* N2 a- Ipsilateral single node 3-6cm* N2 b- Ipsilateral multiple nodes all <6cm* N2 c- Contralateral nodes<6cm* N3- any node >6cm size* M1-metastasis