同位语从句（续） 名词从句（1）
二、由名词从句转变成的同位语从句(实际上在其前面省去了介词of/on/about/as to) The question now arises(出现) whether(是否) this series(级数) converges(收敛). The reader may have no idea what this symbol(符号) stands for(表示). The users(用户) have no guarantee(保证) how long this kind of device(设备) will be operating(工作). Since then(那时), there have been speculations(推测) whether(是否) life(生命) exists(存在) on other planets(行星).
名词从句（1） 一、一般情况 1、引导词 (1) 连接词：在从句中无语法成分 that→无词义 whether→“是否” (2) 连接代词：在从句中有成分 what→“什么”；“…的[内容；情况；话；…]” which→“哪个/本/枝…；哪些” (3) 连接副词：在从句中一般作状语 when→“何时；…的时间” where→“何地；…的地点” why→“为何；…的理由” how→“如何；…的方式/原理”
2、种类 (1) 主语从句(主句谓语必定为单数第三人称形式) That there is only one solution(解) to this equation(方程) is clear(清楚的). Whether(是否) a transformer(变压器) is step-up(升压的) or step-down(降压的) always refers to (涉及) voltage level(电压电平). How large this error(误差) is depends on the nature(性质) of the measuring device(测量仪器) and the measuring skill(测量技巧).
※主语从句也可采用形式主语“it”的句型： 句型A： “it + 连系动词+表语(多为形容词)+主语从句” It is possible that they use this chemical(化学药品) to treat(处理) water. It seems(似乎) strange(奇怪的) that there should be two different kinds of interation(相互作用). It is immaterial(无关紧要的) which letter(字母) we use to represent(表示) the “variable(变量) of integration(积分)”.
It is now clear(清楚的) why the laser(激光器) usually(通常) oscillates(振荡) in this way(方式). It is now a well-known(大家知道的) fact(事实) that all matter(物质) is made up of(由…构成) minute(微小的) particles(粒子).
其中常见的句型如下： (i)“it is necessary that …”→“必须…;有必要…” (ii)“it is possible that …”→“能够…；…是可能的” (iii)“it is clear或evident或apparent或obvious that”→“显然；很清楚” (iv)“it is important that …”→“重要的是…”