There are many websites，________you can find almost all the necessary information.

A．where

B．from where

C．when

D．from when

保温瓶的双层玻璃夹层里被抽成真空，然后加以密封．如果不慎将密封处损坏，保温瓶就不保温了．造成这种不保温的主要热传递方式是 [ ]

A．传导

B．对流

C．辐射

D．无法确定