He gave up the way of life he had got accustomed to ________ to be independent. [    ]

A. learning  

B. learn

C. to learn  

D. to learning

除了ISDN和Cable MODEM外，ADSL也是一种宽带接入方式。它采用不对称的传输模式，其数据下载速度比数据上传速度要【 】得多。