优美的乐曲《梁祝》，既能用小提琴演奏，又能用钢琴演奏。我们能够区别钢琴和小提琴的声音，主要是依据声音的 [ ]

A．音调

B．响度

C．音色

D．频率

Originally introduced by Netscape Communications, （66） are a general mechanism which HTTP Server side applications, such as CGI （67） , can use to both store and retrieve information on the HTTP （68） side of the connection. Basically, Cookies can be used to compensate for the （69） nature of HTTP. The addition of a simple, persistent, client-side state significantly extends the capabilities of WWW-based （70） .

A．fixed

B． flexible

C． stable

D．stateless