The New Mother Is Distressed and Tearful About the Elevated

The new mother is distressed and tearful about the elevated dome over her baby's posterior fontanelle. The nurse's best response is, "This condition will resolve itself in a few days. It is caused by:

A) Prolonged pressure against the partially dilated cervix."
B) Small leak of fluid through the posterior fontanel."
C) Pressure of the forceps during delivery."
D) The effect of the vacuum extractor."