The highlighted part of the sentence is incorrect. The term 'drain off (something)' or 'drain (something) off' means to cause a liquid to flow away from something or to leave the surface of it. The given sentence talks about being tired. So, the phrase doesn't fit in the given sentence. We can also eliminate options (a) and (b) on this basis.
Option (d) is in the simple present tense. Since the sentence is in the simple past tense, the use of the present tense in the phrase is not correct. So, option (d) is eliminated.
Among the given options, the correct choice is ' I felt completely drained out'. The term 'drained out' means 'be deprived of strength or vitality'.
Hence, option (c) is the correct answer.
The correct sentence is: After a long day of work, I felt completely drained out and just wanted to relax at home.