How could he be persuaded to stay?
由can, could和be可构成被动结构，can, could 后的不定式可用完成形式，may，might或should等词后的不定式也可用完成形式。有一些不定式结构如ought to, be going to等也可构成被动形式。有些成语动词如及物动词+副词，动词+介词，动词+副词(名词)+介词等都可以有被动结构形式。
(1) This can't have been done by a human being.
(2) The road may be further widened.
(3) They might have been put in the wrong place.
(4) This ought to be done right away.
语法分析：ought to 的被动结构。
(5) When is the dam going to be completed?
语法分析：be going to 构成的被动结构。
(6) Her illness was brought on by her worries.
(7) We were assigned a lot of homework.
(1) This can't _____ done in a short time.
(2) She might _____ sent to work abroad.
(3) All these factors mustn't _____ neglected.
(4) This should _____ kept a secret.
(5) Does this need _____[be] mentioned?
(6) How many people are going to _____[send] there?
(7) This has to _____[do] promptly.
(8) Not a soul was _____[see].
(9) You are requested _____[present] at the ceremony.
(1) be (2) be (3) be (4) be (5) to be (6) be sent (7) be done (8) to be seen (9) to be present