Answer:
Plural form of the sentence would be:
Police officers enforce the laws of the nations and protect their people.
Step-by-step explanation:
In English, we make the plural form of the nouns by adding the terminations "-s" or "-es" on the singular form of the noun.
Therefore, "a police officer" will pass to "police officers" and "nation" will pass to nations.
The word "laws" is already in the plural, the same as the word "people".
The singular form is "law" and the plural form is "laws".
The word 'people' is singular in writing but plural in meaning. The singular form of this noun could be 'person'.
When it comes to the pronouns, its will pass to their, as "a nation" passed to "the nations."
When it comes to the verbs, they will change into the plural form.