Ring (m) -> Rettungsring (m); Plural: Rettungsringe
"sollen" is a modal verb which is normally complemented by another verb in the infintive (without "zu").


Man soll keinen Rettungsring stehlen.
subject conjugated modal verbdirect object (accusative case) -> masculine singular form of "kein-" in the accusative case infinitive of the past participle "gestohlen"
 
Man soll keine Rettungsringe stehlen.
subject conjugated modal verb direct object (accusative case) -> plural form of "kein-" in the accusative case infinitive of the past participle "gestohlen"

 

 

Man soll den Rettungsring nicht stehlen.
subject conjugated modal verb direct object (accusative case) -> masculine singular form of the definite article in the accusative case negating word infinitive of the past participle "gestohlen"

 

Man soll diesen Rettungsring nicht stehlen.
subject conjugated modal verb direct object (accusative case) -> masculine singular form of the article modifier "dies-" in the accusative case negating word infinitive of the past participle "gestohlen"

 

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