出现下列哪种情况，早期妊娠可能性大

A．停经，早孕反应

B．黄体酮试验撤退性出血阳性

C．基础体温持续高温相超过18天不下降

D．B超可见心血管搏动

E．基础体温呈双相

Coast Guard regulations require that all of the following emergencies be covered at the periodic drills on a fishing vessel EXCEPT（）.

A.minimizing the affects of unintentional flooding

B.fire on board

C.rescuing an individual from the water

D.emergency towing