关于单个核细胞说法错误的是（）

A.单个核细胞包括淋巴细胞、单核细胞

B.单个核细胞的体积、形态、比重与其他细胞不同

C.可利用单个核细胞的体积不同，按照密度梯度来分离

D.在进行密度梯度分离时，单个核细胞比重比溶液的比重大

E.多核粒细胞比重比单个核细胞比重大

Mr. Tiger insisted that he _______ the money back to his boss but his boss said that he didn’t receive it.

A．should pay

B．had paid

C．pay

D．would pay