大全-2-12. Y has been believed to cause Z. A new report, noting that Y and Z are often observed to be preceded by X, suggests that X, not Y, may be the cause of Z. Which of the following further observations would best support the new report’s suggestion? (A) In cases where X occurs but Y does not, X is usually followed by Z. (B) In cases where X occurs, followed by Y, Y is usually followed by Z. (C) In cases where Y occurs but X does not, Y is usually followed by Z. (D) In cases where Y occurs but Z does not, Y is usually preceded by X.（A）
(E) In cases where Z occurs, it is usually preceded by X and Y.
是不是很傻的问题，快考试了，可是我还是不太理解：A follow B, A precede B 是什么意思，前后是指早还是晚呢？ | 
