Which of the following is correct? both David, be sure to mind your ps and qs. David, be sure to mind your p's and q's.

Attempts at explaining the origin of the phrase go back to the mid-19th century. One explanation favoured in a letter to the editors of Notes and Queries dated 1851, is a literal interpretation of the saying, regarding the lowercase letters p and q in the context of the school-room or typesetting in the printing-office. This is given as a common suggestion by the 2007 revision (3rd edition) of the Oxford English Dictionary, but the OED considers the explanation unlikely since the chronology of the senses would argue against this, and no such connotation is evident in the earliest quotations and says that the origin of the expression is unknown

the answer should be d) he was one of those young thousands who greeted the war with a certain amount of relief, welcoming the liberation from webs of tangled emotion" since it is the best option because it shows his desire to free himself. 

hope this answer you! have a great day.