答案：C

题目分析：句意：你愿意帮我打开电视吗？——当然，我愿意。 A.No,please not 不，请不要；                    B.Sorry,I don’t对不起，我不会；  C.Certainly,I will do it 当然，我愿意。 D.Yes,please do是的，请。对Will you please do sth.？的肯定回答是Yes/Certainly,I will do it . 否定回答是No/Certainly not, I will not do it .故选C。