You need to answer a given question containing a blank (_). Your answer must be one of the two objects mentioned in the question, for example "trophy" and "suitcase". Your answer must not contain a word that is not present in the question. Please don't use articles (e.g., the, a) before the answer.

The drifter pulled out his harmonica while riding the train and played a tune over the _ noise.
train

While taking classes at the college, Sam bought the textbooks she needed and returned the notebook she didn't. The _ were necessary.
textbooks

The caterpillar tried to build its cocoon on the leaf, but the _ was too fragile.

leaf