胸腺依赖淋巴细胞是指( )
A.T细胞B.B细胞C.NK细胞D.K细胞E.树突状细胞(DC)
参考答案:A
二次函数y=x2+2的图象开口( ),对称轴是( ),顶点坐标是( )。
The eastern part of the country is much more developed ____the western part is poorer.
A.which B,that C,while D,as