6. 某碳酸(H2CO3)水溶液的濃度為0.00372M,若已知碳酸於室溫時之Ka1=4.3×10-7及 Ka2=5.6×10-11,則該水溶液中[CO32-]為多少M? (A) 5.6×10-11 (B)4.3×10-7 (C)4.0×10-5 (D)0.00372