To complete Alisa's answer.
问:这个真的是你亲手做的吗?
答:是呀~! (是的、是啊) These three answers are all okay. I use randomly one of them.
问:这么好吃的菜是你一个人独立完成的?
答:对呀~!(对的,对啊)These three answers are all okay. I use randomly one of them.
问:你旁边这个位置没人的话,我可以坐下吗?
答:可以呀。(可以啊)
问:这道题我做对了吗?
答:对啦~!(对呀)
问:刚才买的薯条还有吗?
答:早就吃光啦~!(早就吃光了)
In most cases, they are interchangeable.