遇到巨大声响时,可迅速张嘴,使咽鼓管张开;或闭嘴同时双手堵耳,保持____ 两侧大气压力平衡,以免损伤鼓膜.
—I am very ____ tomorrow's Math test . I am afraid I can't pass this time.
—Cheer up! I'm sure you'll make it.
如图,图中文艺复兴时期作家的表述,体现了什么思想或精神?( )
下列装置或操作能达目的是( )