— What _____________ to the young tree yesterday?

— Its leaves falled.[ ]

A. happen

B. happens

C. happened

D. happening

关于新生儿败血症的实验室检查，下列哪项结果提示没有诊断或帮助诊断价值（）

A.血培养提示有细菌生长

B.白细胞总数8×10/L

C.每100个中性粒胞中杆状核细胞≥20个

D.血沉＞15mm/h

E.CRP为15μg/ml