constbird={size:'small'}constmouse={name:'Mickey',small:true}A:mouse.bird.sizeB:mouse[bird.size]C:mouse[bird["size"]]D:都是有效的参考答案：
constbird={size:'small'}constmouse={name:'Mickey',small:true}A:mouse.bird.sizeB:mouse[bird.size]C:mouse[bird["size"]]D:都是有效的参考答案：