已知PbI₂的K_sp=7.0×10^-9，将7.5×10^-3 mol/L的KI与Pb（NO₃）₂溶液按体积比为2：1混合，则生成PbI₂沉淀所需Pb（NO₃）₂溶液的最小浓度（mol/L）为（　　）

A．8.4×10^-4

B．5.6×10^-4

C．4.2×10^-4

D．2.8×10^-4

---It cost me 30 yuan to get here.

---Well, it was crazy of you to take a taxi        you would come by bus as well.

A．unless

B．when

C．if

D．because