(1) A 'murmur' is a low, indistinct sound made by many people, which fits the context of excited whispers spreading through a classroom. (2) To 'sigh' is to emit a long, deep breath expressing relief, which fits the context of Anaya feeling relieved that the challenge involves riddles rather than Mathematics. (3) To 'whisper' is to speak very quietly, which creates suspense and encourages students to pay close attention. (4) To 'groan' is to make a deep sound expressing disappointment or dismay, which fits students realizing the question is difficult. (5) 'Snickers' are suppressed laughs or giggles, which fits students quietly laughing or commenting among themselves about the difficulty of the question. (6) A 'thud' is a dull, heavy sound like that made by a book hitting a desk, fitting the context of tapping a book. (7) A 'groan' can also express effort or strain, fitting the context of stretching after mental effort. (8) To 'rattle' means to make a rapid series of short, sharp sounds, which windows make when shaken by wind. (9) To 'mumble' is to speak indistinctly, which fits students speaking quietly or unclearly in their eagerness to know the answer. (10) To 'whisper' is to speak softly, which creates a dramatic effect when revealing the answer.