参考答案

正确答案：A
解析：词汇题。含有此词汇的句子是Science cannot really explain electricity，magnetism，and gravitation；their effects can be measured and predicted，but of their nature no more is known to the modern scientist than to Thales who first speculated on the electrification of amber。本句的意思是，科学不能真正解释电、磁、重力；它们的效果能被测量和预测，但是它们的本性对现代科学家和第一个对琥珀带电现象进行思考的Thales一样是不可知的。所以正确答案是A选项。