你问的是it's +形容词 for/of sb to do sth 结构中吧如果形容词能表示【人的本质】，用of，反之用for。例如：我们可以说： You are kind/ friendlyIt's kind /freindly of you to do sth我们不能说：You are difficult/easyIt's difflcult for you to do sth.不懂续问。
