In each of the following questions, the sentence is broken into four parts labelled (P), (Q), (R) and (S). You are required to arrange these parts so as to form a complete meaningful sentence and then choose the correct combination (Qs. 2৬ - 3০).

You must leave a note
P: otherwise she will be terribly worried
Q: for your mother
R: at the usual hour
S: if you are not back home