Assessment of a client in active labor reveals meconium-stained amniotic fluid and fetal heart sounds in the upper right quadrant. Which of the following is the most likely cause of this situation

A. Breech position.
B. Late decelerations.
C. Entrance into the second stage of labor.
D. Multiple gestation.

采用瓦斯统计法进行区域预测时，应根据已开采的区域确切掌握的（）与突出分布的规律，划分出突出危险区和非突出区。