“德意志民族曾经号称‘思想家和诗人的民族’，也涌现出了一流的科学家和艺术家。……但是，这个伟大的民族有曾在一个狂人的操纵下进行过最骇人听闻的大屠杀。”后者产生的历史根源是

Besides calling 120, here is what you should do when no one is around to help.

If you get lost, you may stay where you can be seen clearly and try your best to have a rest. In a wide open area, make a colorful cross out of rocks to show where you stay.

When you choke at home, make a sudden hit against the back of the chair. If you can't breathe after six tries, call 120. Leave the telephone open until help arrives.

Use your hand or a scarf, or any dry cloth you can find, and push down on the wound until the blood stops running. Don't put the cloth around your leg tightly(过紧), or you may lose your foot.

When a fire breaks out, you must move close to the floor. Cover your mouth and nose with a wet towel, make you wet from head to foot if possible and find a safe place outside.

兴趣小组的同学要测量树的高度．在阳光下，一名同学测得一根长为1米的竹竿的影长为0.4米，同时另一名同学测量树的高度时，发现树的影子不全落在地面上，有一部分落在教学楼的第一级台阶上，测得此影子长为0.2米，一级台阶高为0.3米，如图所示，若此时落在地面上的影长为4.4米，则树高为　____ ．