表面活性剂之所以能降低表面张力,是由其结构特征决定的。()
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新洁尔灭为常用的阴离子型表面活性剂。()
A. 对
B. 错
Listentothepassageagainandfillintheblankswithwhatyouhear.[音频]Reasonsfor homeschoolingSomeparentsworrythattheirchildren1) ____________ inschoolbecauseof schoolbullying.Someparentswanttheirchildren‘seducationtobebasedontheir 2) ____________________.Someparentsfeelschooleducationis3)________________________.Homeschoolingisachoiceforfamiliesthat4) ______________________ orthatoften travel.Waysof homeschoolingHomeschoolingallowsparentstopersonalizelessonsaccordingtotheirchildren’s needs.Parentscanbuytextbooksor5) _______________________.Someparentsallowchildrentodetermine6) __________________ basedontheir naturalcuriosity.Somefamiliesarrangeagroupofhomeschooledstudentsto7) ___________________________andparticipateinactivitieslikefieldtripsanddancingparties.
当硅二极管加上0.4V电压时,该二极管相当于( )
A. 很小的电阻
B. 很大的电阻
C. 短路
D. 电容
加在硅二极管上的正向电压大于死区电压时,其两端电压( )
A. 随所加电压增加而变大
B. 随所加电压增加而减小
C. 为0.7V左右
D. 为0.3V左右