Answer: D."Increased vasocongestion of the pelvic muscles causes a bluish discoloration of the mucous membranes of the cervix, vagina, and vulva, known as Chadwick's sign. A positive pregnancy test is considered a probable sign of pregnancy because the similarity of HCG and LH occasionally results in cross-reactions, potentially leading to a false positive result. Increased vascularization results from hypertrophy and engorgement of the vessels below the growing uterus, thus producing softening of the cervix, known as Goodell's sign. Probable signs of pregnancy are objective changes that occur in pregnancy."