【单选题】Why does an astronaut put his hand under his belt when he sleeps?
A.
Because he thinks it is comfortable to sleep in that way in space.
B.
Because he doesn't want to touch any controls when he sleeps.
C.
Because the instruments of the spaceship are easily broken.
D.
Because he is afraid that the seat will move.
【简答题】如图所示,在△ABC中,∠C=90°,BD平分∠ABC交AC于点D,过点D作DE ∥ BC交AB于点E,过点D作DF⊥AB于点F,请回答下列问题. (1)DE与BE相等吗?请说明理由; (2)判断BC,DE,EF三者的数量关系,并说明理由; (3)平行线DE,BC之间的距离与DF的长度有何数量关系,为什么?
【单选题】Why does an astronaut put his hand under his belt when he sleeps? 查看材料
A.
Because he thinks it is comfortable to sleep in that way in space.
B.
Because he doesn’t want to touch any controls when he sleeps.
C.
Because the instruments of the spaceship are easily broken.
D.
Because he is afraid that the seat will move.
【简答题】试说明利用甘特图进行作业排序的优势以及局限性。
【单选题】胃肠道平滑肌的紧张性和自动节律性主要依赖于
【单选题】如图所示,已知CD⊥AB,BE⊥ AC,垂足分别为D、E,BE、CD相交于O点,∠1=∠2,图中全等三角形共有 [ ]