North Korea has always sought for a direct talk with the US, without China ________.

A．involving

B．to involve

C．involved

D．be involved

无论脑膜是否有炎症，在脑脊液中均具有较高浓度的抗微生物药物有____，在脑脊液中可达到有效杀菌或抑菌水平。