问题 选择题

下列说法正确的是:(  )

A.一块砖切成体积相等的两块后,砖的密度变为原来的一半。

B.铁的密度比铝的密度大,表示铁的质量大于铝的质量。

C.铜的密度是8.9×kg/m表示1立方米铜的质量是8.9×kg.

D.密度不同的物体,其质量一定不同。

答案

答案:C

题目分析:密度是物体的特性,与物体的质量和体积无关,所以一块砖切成体积相等的两块后,砖的密度不变,A不符合题意;铁的密度比铝的密度大,表示相同体积的铁比铝的质量大,B不符合题意;C表述为密度的物理意义,C正确,密度不同的物体,质量可以相同答案D错误,所以答案选C。

单项选择题
单项选择题

I got a job teaching special education at a school in Coachella, California, a desert town about 170 miles from home. It was no (1) job. Street gangs (2) around the school after dark."Be careful," Dad warned me during one of my frequent weekend (3) home. He was concerned about my living (4) , but I needed to be on my own.One evening, I stayed after school to rearrange my classroom. (5) , I turned out the light and closed the door. Then I (6) toward the gate. It was (7) ! I looked around. Everyone had gone home.After (8) all the exits, I found just enough (9) to squeeze under a gate in the back of the school. Then I walked toward my car, parked in a field behind the building.Suddenly I heard voices. I (10) around and saw at least eight boys following me. (11) my pace, I reached into my shoulder bag to get my key. I (12) all over the inside of my handbag. But the key wasn’t (13) ! Dear Lord, please help me, I prayed (14) . Suddenly, my fingers touched a loose key in my purse. I didn’t even know if it was for my car, but I took it out and (15) it. It worked!I opened the door, slid in and locked it—just (16) the teenagers surrounded the car. Trembling , I started the engine and (17) away. When I returned to my apartment, the phone was ringing. It was my Dad. I didn’t tell him about my experience; I didn’t want to (18) him. "Oh, I forgot to tell you!" He said, "I had a(n) (19) car key made and slipped it into your purse—just (20) you ever need it.

第(4)空应选择()

A.happily

B.far

C.nearby

D.alone