单选题

下面哪个能正确定义一个 Objective-C 类？

Question

A. @class ClassName : ItsSuperclass { instance variable declarations } method declarations @end

B. @interface ClassName : ItsSuperclass { instance variable declarations } method declarations @end

C. @class ClassName : ItsSuperclass { instance variable declarations method declarations } @end

D. @implementation ClassName : ItsSuperclass { instance variable declarations } method declarations @end