have you decided what you ___ on sunday?---Not yet,but i___

chose d,
first,the question asked that you do something on sunday,it must be something you have to do in the future,so you should chose "are going or will do",second,"going to do "is a future tense,and the word "think"is a momentary word,so you must chose "be thinking",to sum up,you should chose d.that's all

D on sunday 是过去式， so 用will do
am thinking 我正在想

First
这么打才对哟

我晓得：D on sunday 是过去式， so 用will do
am thinking 我正在想

D
decided 后面跟的内容都是将来发生的，由此可以排除A、C，think 表示是现在正在进行的动作，所以用使用现在进行时，排除B。