Rose usually wakes up early in the morning. She always has her breakfast at half past six. She leaves home at about seven o’clock.. She is never late for school.
    She has many classes in the morning. At about twelve fifteen, she comes back for lunch. In the afternoon, she isn’t so busy. After school she   does her homework and plays with other children.
    In the evening, her parents come back from the factory. The family has supper together. After that, they usually read newspaper or listen to the radio for a little time. Sometimes, they watch TV. Rose goes to bed at half past nine. But her father often works late at night.

经常锻炼身体，这样有利于身体健康。（ ）

如图，两根电线杆相距Lm，分别在高10m的A处和15m的C处用钢索将两杆固定，求钢索AD与钢索BC的交点M离地面的高度MH．