The correct passive form of the given sentence "People speak Cantonese in Hong-Kong" is Cantonese is spoken in Hong-Kong.

The active voice of the sentence is "People speak Cantonese in Hong-Kong." This sentence is in the present simple tense, which is used to describe an action that happens regularly or happens now. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the present participle of the main verb. In this case, the subject of the active sentence is "Cantonese" and the main verb is "speak." The present participle of "speak" is "speaking." So, the passive form of the sentence is "Cantonese is spoken in Hong-Kong."

The other options are incorrect because:

• Cantonese was spoken in Hong-Kong." This sentence is in the past simple passive voice, which is used to describe an action that happened in the past. However, the action of speaking Cantonese in Hong Kong is still happening now.
• Cantonese was spoken in Hong-Kong by people." This sentence is in the past simple passive voice with the agent "by people" added. The agent is the person or thing that is doing the action. However, the agent is not necessary in the passive voice, and it can be omitted.
• Cantonese is being spoken in Hong-Kong." This sentence is in the present progressive passive voice, which is used to describe an action that is happening now but is not finished. However, the action of speaking Cantonese in Hong Kong is not happening now.