In each of the questions given below, read each sentence to find out whether there is any grammatical error in it. The error, if any, will be in one part of the sentence. Mark the part with the error as your answer. If there is no error, mark ‘No error’ as your answer (Ignore the errors of punctuation, if any).
A. Every morning, he goes for a thirty-minute 
B. walk in the park to stay healthy and clear 
C. his mind before start his busy workday
D. with full energy and focus.