Select the option that expresses the given sentence in passive voice.

The rules forbid passengers to cross the railway bridge.

Passengers are forbidden by the rules to cross the railway bridge.

The correct passive voice of the given sentence is Passengers are forbidden by the rules to cross the railway bridge.

The active voice of the sentence is The rules forbid passengers to cross the railway bridge. This sentence is in the simple present tense, which is used to describe an action that is happening now or that is happening repeatedly. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the past participle of the main verb. In this case, the subject of the active sentence is "the rules" and the main verb is "forbid." The past participle of "forbid" is "forbidden." So, the passive form of the sentence is Passengers are forbidden by the rules to cross the railway bridge.

The other options are incorrect because:

• Forbidden are the passengers to cross the railway bridge. is in the active voice, but it does not use the verb "to be."
• Forbidden by the rules, the passengers cannot cross railway bridge is a jumbled sentence that does not make sense.
• Railway bridge is forbidden for the passengers to cross. is in the passive voice, but it does not specify who is forbidding the passengers from crossing the bridge.
• Forbidden passengers to cross the railway bridge. is the active voice of the original sentence, not the passive voice.