下列哪些特性与SN2反应符合? (1)反应速率只取决于亲核试剂的浓度, (2)亲核试剂从离去基团的反面进攻, (3)反应过程中键的形成和键的破裂同时发生。
A. 1和2
B. 1和3
C. 2和3
D. 全部都是
At present, E-Commerce platforms mainly adopt three types of logistics and they are ( ).
A. enterprise self-support logistics
B. outsourcing logistics
C. Logistics Enterprise Alliance
D. social integrated logistics