同一主族氢化物的熔沸点随分子量的增大而升高,因此按沸点高低排序:H2O<H2S<H2Se。( )
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??Some people believe that using a DNA fingerprint may not be so reliable because??
A. the accuracy of DNA fingerprinting has been challenged
B. no private laboratory foIloWs uniform. testing standards or quality controls
C. mistakes are possible when researchers explain the results of their tests
D. suspects may not have enough money to provide their own DNA to law-courts
SVD狙击步枪可以说是狙击枪家族中的元老级人物,资历极其____,上过越南战场,经历过两伊战争,在阿富汗、黎巴嫩、车臣留下过____,参加过沙漠风暴行动和伊拉克战争,功勋____,成绩斐然。
填入划横线部分最恰当的一项是:
A. 丰富 足迹 卓著
B. 雄厚 踪迹 显赫
C. 抢眼 身影 卓越
D. 深厚 痕迹 卓然
The land crab a forest-floor scavenger native to tropicalAmerica, migrates to the water
A. die
B. swim
C. mate
D. hatch