Which of these is an occurrence of stage one of parturition? A: Animal strains and pushes
B: Fetal membranes are released
C: Respiratory rate of mother increases
D: Uterus and abdominal muscles all contract

I personally think it's D but I would love some feedback <3

Dilation of
Stage 1: The first stage of parturition is dilation of the cervix. The normal cervix is tightly closed right up until the cervical plug is completely dissolved. In stage 1, cervical dilation begins some 2 to 24 hours before the completion of parturition (2 to 6 hours would be most common).

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