以下哪一项是启动jQuery插件的方法？

Question

$.fn.plugin = function() {this.css(“color”,”black”);}; 

function plugin() { this.css(“color”,”black”); };

var plugin = function( a, b ) { this.css(“color”,”black”); };

$.plugin = function() {this.css(“color”,”black”);}; 

${}.plugin = function() {this.css(“color”,”black”);};