91025
Reaching back even further , since the fetus has an active auditory system 3 – 4 months before birth , the rhythm of the mothers womb and the sound of her heartbeat could be the start of our responsiveness to music .
 fetus
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 fetus