Final answer:
The appropriate term for the softening of the cervix and vagina as a sign of pregnancy is Goodell's sign.
Step-by-step explanation:
The nurse is referring to Goodell's sign, which is the softening of the cervix and vagina that is a probable sign of pregnancy. The softening of the cervix typically occurs around the fourth or fifth week of pregnancy. The correct answer to the question 'The nurse explains that the softening of the cervix and vagina is a probable sign of pregnancy. What is the appropriate term for this sign?' would be 4) Goodell's sign.