Step 1: Identify the opening idea.
P states a general truth: "Children need to be loved, and in a sense they cannot have too much of it." This works well as an opening line because it introduces the theme of love and children before anything specific is discussed.
Step 2: Find the sentence that introduces a contrast.
S says: "But it is not because of love that a mother prevents her child from growing up." The word "But" signals a contrast with the idea just introduced in P, so S must directly follow P.
Step 3: Identify what explains the real reason.
Q says: "She herself doesn't want to grow up and attempts to make time stand still." This explains the real reason behind the mother's behavior that S just said was NOT about love. So Q naturally follows S.
Step 4: Identify the concluding remark.
R says: "Fortunately she cannot succeed." This is a closing comment on the mother's attempt described in Q, so it comes last.
Step 5: Assemble and match.
The order P-S-Q-R forms a coherent short passage: children need love; but a mother who won't let her child grow up isn't doing it out of love; she doesn't want to grow up herself and tries to freeze time; fortunately, she fails. This matches option (a), PSQR.