题目

根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。 If something that you're doingdoesn't challenge you, then it doesn't change you. We all need some normalstress in our lives, after all. So challenge the following limits: ⒈Figure out what you're scaredof and do it continuously.If you're a salesman, andyou're scared of talking to people personally or over the phone now, instead ofbeing scared and thinking you'll fail, spend at least five minutes a day topick up the phone and make a call. But don't stop on the first try! Eventually,you can look at fear 鉴别空气、氧气和氮气三瓶气体时的最佳方法是（ ）A．测量三瓶气体的密度B．测量气体的溶解性C．用带火星的木条分别伸入三瓶气体中D．用燃着的木条分别伸入三瓶气体中