The scientists believe ( )they have devoten themselves to ( ）sure to come true.a.that all ,are b.what,is 选项是b.what=the thing which/that如果我的回答对你有所帮助,请点击本页面中的“选为满意回答”按钮...为什么不选a？The scientists believe ( )they have devoten themselves to ( ）sure to come true。a. that all ,are b.what,is如果a选项的are改成is也是正确的。因为all在此句中做主语是单数。如果我的回答对你有所帮助，请点击本页面中的“选为满意回答”按钮，谢谢！