Question

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

Answer 1

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