ok my thoughts: I would most certainly get rid of answers a and d for we should change the word order. And my doubts are as follows I would choose answer c - which for me has a general meaning, do you know when your father (usually) arrives. In b it would probably mean that today he will come at a certain time, please help me sort this problem out.
Thank you for you help, but let me just see if I understood correctly. So, if the plans are definite then c would be ok, but generally the times of the father's arrival differ, right?
Thank you for you help, but let me just see if I understood correctly. So, if the plans are definite then c would be ok, but generally the times of the father's arrival differ, right?