患者，男，54岁，右舌缘溃疡5个月不愈，全身一般情况良好。门诊活检诊断为"舌鳞状细胞癌（Ⅱ～Ⅲ级）"。经专家门诊详细检查后诊断为"右舌缘鳞状细胞癌（T3N2aM0）"。

N2a的意思是指（）

A.同侧单个淋巴结转移，直径＞3cm，但＜6cm

B.同侧单个淋巴结转移，直径≤3cm

C.同侧半个淋巴结转移，直径＞6cm

D.多个同侧淋巴结转移，直径＜6cm

E.同侧或对侧淋巴结转移，直径＜6cm

Which of the following is NOT the purpose of America’s central bank

A．Controlling the flow of money in the economy.

B．Overseeing the activities of banks.

C．Producing and distributing bank notes and coins.

D．Contributing to the maintenance of a stable financial system.