声音的三个特性是音调、 ____和 ____;弹吉它时,用力拨琴弦时,琴弦的振幅较大,所以发声的 ____较大 。
Besides calling 120, here is what you should do when no one is around to help.
If you get lost, you may stay where you can be seen clearly and try your best to have a rest. In a wide open area, make a colorful cross out of rocks to show where you stay.
When you choke (噎住) at home, make a sudden hit against the back of the chair. If you can't breathe after six tries, call 120. Leave the telephone open until help arrives.
If you get hurt, use your hand or a scarf, or any dry cloth you can find, and push down on the wound(伤口) until the blood stops running. Don't put the cloth around your leg tightly, or you may lose your foot.
When a fire happens, you must move close to the floor. Cover your mouth and nose with a wet towel (毛巾), make you wet from head to foot if possible and find a safe place outside.
①认识能否达到最终目的受到特定社会历史条件的制约
②现代科技手段的运用推动了有关恒星团认识的深化发展
③人类的好奇心是推动科学研究深入发展的源泉和动力
④理论完善和认识能力的提高是科学实践成功的首要因素
水银气压计若挂歪了,其读数将会( )