A. Only transitive verbs may be changed to passive forms.

- The ship has been disappeared. (incorrect)
- English is spoken here. (correct)

B. Verbs like make, tell, and ask are followed by a to-infinitive in passive sentences.

- The boys were made to work very hard.
- The girls were asked to stop laughing.

C. Perceptual verbs like see, observe, and hear are followed by either a to-infinitive (for repeated or habitual actions) or an -ing form (for an action in progress) in passive sentences.

- The geese were observed to fly south every autumn. (habitual)
- The geese were seen swimming in the pond. (action in progress)

D. Complex verbs that consist of verb + preposition are treated as one unit when changed to passive.

- They laughed at him. -* He was laughed at (by them).
- Nobody has slept in this room. -* This room has not been slept in (by anybody).

E. Besides by, the prepositions at and with may also be used in passive sentences.

At: be alarmed at, be surprised at

With: be pleased with, be satisfied with, be covered with, be (pre)occupied with

At or With: be delighted at/ with, be disgusted at/ with