问题
补体活化经典途径的C3转化酶为A．C3aB．C5bC．C4a2aD．C4b2bE．C567
补体活化经典途径的C3转化酶为
A．C3a
B．C5b
C．C4a2a
D．C4b2b
E．C567
请帮忙给出正确答案和分析，谢谢！
Fatal error: Uncaught [XSException] ../../../usr/local/xunsearch/sdk/php/lib/XS.php(2559): Connection refused(C#111, localhost:8384)
thrown in /usr/local/xunsearch/sdk/php/lib/XS.php on line 2559
