被…所【bèi…suǒ】

被…所 is the 被 passive with 所 placed before the verb. The meaning doesn't change; the register does, and the sentence reads like an essay or a news report. The verb is usually two syllables.

The doer must be named

Plain 被 can leave the doer out: 他被批评了. Once 所 is added, the doer has to stand between 被 and 所.

• × 这种方法已被所采用 → 这种方法已被很多学校所采用 / 这种方法已被采用

The verb ends the clause

被…所 closes on its verb. A sentence that needs a complement, an amount or an object after the verb goes back to plain 被.

• × 他被老师所批评了一顿 → 他被老师批评了一顿
• × 我被这本书所吸引住了 → 我被这本书吸引住了

Negation

没有 or 不 goes before 被.

被…所 or 为…所

为…所 is the older, more literary form; 被…所 is what modern reports and essays mostly use. They take the same verbs, and 为…所 has its own entry.