（4）状语 （其逻辑主语一般就是句子的主语）
A. 在主语前（用“试探法”来确定其确切的含义，以“原因”和“对主语或后面句子的补充说明”为多见） Accurate(精确的) in operation(运算) and high in speed, computers can save man a lot of time and labor(劳力). Free from(不受) the attack(侵蚀) of moisture(潮湿), a piece of iron(铁块) will not rust(生锈) very fast. Large or small, all circuits(电路) contain(包含) the same kinds of components(原件).
Contrary(相反的) to common(普通的) belief(信念), forces(力) are not transmitted(传递) only by “direct contact”(直接接触). 为了学习下次课上的一个句子作准备，讨论一下“but”和“expose/exposure”的常见含义： Air is not visible(可见的), but it is matter(物质). An element(元素) is made up of(由…构成) but one kind of material. We cannot discover(发现) any material(物质) in an element but itself.
This roll of film(胶卷) has been exposed(暴露) to light. This book should be useful in exposing computer scientists to the latest(最新的) technology(技术). Excessive(过度的) exposure to X-rays is harmful(有害的) to one’s health(健康). Prior(先前的) exposure to advanced(高等的) mathematics is required(要求).