题目

Are you truly happy? Do you ever know what it means to be happy and what it takes to achieve happiness? __36___. The following are a few tips that I follow to create happiness in my life. ※ Make a plan for achieving goals that you believe will make you happy. Your moods will very likely increase if you are going after something you value. ※Surround yourself with happy people. It is easy to begin to think negatively when you are surrounded by people who think that way. ___37___.   ※When something goes wrong, try to figure out a solution instead of being absorbed in self pity.在学过质量后，甲、乙两同学为了验证空气具有质量，找来了两只大塑料瓶（其中右侧塑料瓶带自行车进气阀），0.5m长的薄木片，打气筒和细绳，做成如图的装置，调整悬点，使木片保持平衡．然后用气筒往进气阀中打气，再关紧气阀．（1）图中运用了______的原理；（2）打气后发现木片向______倾斜，从而说明空气具有质量；（3）我们学过由于大气重力而产生的物理量是______；（4）请估算一间教室内空气的质量______A、2Kg      B、20Kg      C、200Kg       D、2000Kg．