單項選擇題某水生生態(tài)系統(tǒng)調(diào)查時,采用黑白瓶法測定初級生物量。初始瓶IB=5.0mg/L,黑瓶DB=3.5mg/L,白瓶LB=9mg/L。則凈初級生物量和總初級生物量分別為()。

A.5.5mg/L,4mg/L
B.4mg/L,5.5mg/L
C.1.5mg/L,4mg/L
D.1.5mg/L,5.5mg/L