During the stage of birth (which is called the "descent and emergence of the baby" stage), the mother bears down hard to push the baby out of her body; this stage typically lasts 45-60 minutes.

Second

Explanation:

Childbirth involves three stages:

The first stage starts with the onset of true labor and lasts until the cervix is completely dilated to 10 cm.

The second stage continues after the cervix is dilated to 10 cm until the delivery of your baby. This stage is called the "descent and emergence of the baby" stage.  It involves the pushing by the mother and the delivery of your baby. Now that your cervix has fully dilated to 10 cm, this is the time for mother to help by pushing. This stage can last from 20 minutes to 2 hours.

The third stage involves the delivery of the placenta.

answer: - few nutrients

high pressure

low temperatures

explanation: 1. few nutrients:   open-ocean zone is located way far from the land, which is the main source of the essential nutrients.2. high pressure: pressure increases by 1 atmosphere for every 10 meters increase in depth.3. ample sunlight: a large fraction of the sunlight is reflected back to the atmosphere from the sea surface. 4. varying salinity: below the thermocline, the water is isolated from the atmosphere so the salinity remains stable over the year.5. low temperatures:   the temperature of open-ocean zone ranges from a low of -2°c to an average of 17°c