On the morning of October 25, we began an around-the-clock birth watch. Finally, late in the Antarctic evening, we spotted a seal in labor. In less than three minutes, we were on the scene with cameras, temperature probes, and a tape recorder.

The labor lasted for 27 minutes. The mother lay on her side, head and rear flippers extended. Occasionally, she twisted her hindquarters to and fro. During this period there were twelve series of contractions, lasting from 6 to 75 seconds. During the last 70 seconds, the head and shoulders of the pup, encased in a pink membrane, slowly emerged, advancing and retreating with the rhythm of the contractions. With half the body visible, the membrane broke. All at once the pup slid onto the ice, warm and soaking wet into a world 102 degrees colder than the 99 degrees within its mother's body.

Q. Underline the sentence which suggests that seals undergo labor pains prior to giving birth.