如图所示，物体在恒力F作用下处于静止，则下面对物体受力情况的分析正确的是（   ）

乙炔是一种重要的有机化工原料，以乙炔为原料在不同的反应条件下可以转化成以下化合物．完成下列各题：

下列有关实验的描述或操作错误的是(　　)

①追求真理是一个永无止境的过程   
②事物发展是一个辩证否定的过程

③创新是社会发展和变革的先导     
④观念创新可以促进事物价值的转换

阅读理解。   

     My name is Xiaoming. I get up at half past six. I have breakfast at seven o'clock. I go to school at eight o'clock. I have lunch at twelve o'clock. I go home at four o'clock. I have dinner at five o'clock. I watch TV at half past six. I do my homework at seven o;clock. I go to bed at nine o'clock.