1999年3月，甲、乙签订合同。甲将房屋租给乙，月租金2万元，每月月末交付。合同生效后，甲交付房屋给乙。至月底，乙以资金周转不畅，要求缓交租金，甲提出可以宽缓15天。此后，乙始终以种种借口拖延，至8月末，乙总计拖欠房租12万元。下列陈述正确的是：（）

A．甲只能采取一种救济手段：要求乙承担延期交付的违约责任 

B．甲可以直接解除合同，无须征得乙同意也无须通知乙，并可以要求乙承担延期交付的违约责任 

C．甲可以提出解除合同，但须征得乙同意 

D．甲可以提出解除合同，但须通知乙，合同自通知到达乙时解除

Even though current technologies make the ultimate segmented network impractical, new technologies and products hold the promise of making the concept a reality. Most important of all these new technologies are (71) . The ultimate switched LAN, which is technically possible, now, exhibits the following characteristics:
1. High-speed yet cost-effective switching devices can be implemented on a wide scale, providing dedicated connections for individual users and supporting the aggregate (72) of all networked users.
2. The ability to deploy switching capabilities incrementally into the (73) base. Switching implementations support switching of individual users or groups so that existing users of shared media modules can continue to use the existing equipment until they can justify moving to dedicate switched LAN connections.
3. Support and enhancement of existing routed environments. Switching (74) routint, but rather can be introduced into the network without making any changes to the existing routing equipment or configuration. (75) play a critical role in the integration of switching into existing networks.

A. RoutersB. Devices C. I/O D. DSP