题目

如图为显微镜结构图，请根据图回答下列问题。注：“[ ]”表示先填序号在“[]”中，再填序号所对应的名称在“”上。 （1） 转动时，镜筒的升降幅度很大的结构是[ ]。 （2） 取显微镜时，握镜的部位是[ ]。 （3） 把玻片放在[ ]上后，要用[ ]将标本固定住，标本要正对[ ]的中央。 （4） 使用显微镜，应先用倍镜，再用倍镜观察 （5） 在观察物像时发现视野较暗，可采用或，使视野变亮。 若物像在视野的左上角，要把 阅读理解 　　There are many problems connected with space travel．The first and greatest of them is gravity(重力)．If you let your pencil drop to the floor, you can see gravity in action．Everything is held to the earth by the force, which can be described by its weight．A rocket must go at least 2500 miles an hour to take anyone beyond the gravity of the earth into space． 　　Another problem is the strainthat a person feels when a rocket leaves the ground．Anything that is not moving tends to keep still．As the rocket leaves the ground, it pushes upwards strongly and the person in it is pushed back against the chair．Gravity gives the body a force equal to nine times its normal force． 　　Once out of the earth’s gravity, an astronaut is affected by another problem, weightlessness．Here, if a pencil drops, it does not fall．If a glass of water is turned upside down, the water will not fall out．All of us are used to gravity．Recent long flights have shown that the body needs special exercise in a spaceship． (1) The weight is ________ the force gravity gives the object． [　　] A． different from B． morn than C． less than D． as much as (2) When a running car stops, the person in it is pushed ________． [　　] A． forward B． upward C． backward D． downward (3) The passage mainly talks about ________． [　　] A． space travel B． pleasure in spaceships C． problems in space travel D． gravity of the earth