【问】 John was frightened by the new methods。本句中by是引出施动者，还是表示手段?

【答】 分析这个有歧义的句子，有助于我们深入了解by的意义和用法。大家知道，by的最常见用法是在被动句中引出施动者：

This ability was first noticed by her father. (New Concept English，Book 4，P. 14)她的这种能力首先是由她父亲发现的。

但是，by也常常用来表示做某事的手段(If you do something by a particular thing，youdo it using that thing.)例如：

1. The money will be paid by cheque...

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2. You have to express the thought by action.

你必须用行动来表达你的思想。

照此看来，你提出的句子可以有两种解释：

(a)有人用这些新方法来恐吓约翰。(Someone frightened John by the new methods.)

(b)约翰被这些新方法吓坏了。(The new methods frightened John.)

同样，下面的句子也可以有两种解释：

Coal has been replaced by oil.

(a)煤被石油所取代。(Oil has replaced coal.)

(b)人们用石油来代替煤。(People have replaced coal by oil. )