Question

the cow is useful ---man appropriate preposition

Answer 1

Answer:

FOR

The cow is useful for man

Answer 2

The cow is useful for man.

Prepositions are those words which are used to combine nouns, verbs, phrases etc. Examples : for, of, at, on, in, beside, beneath, across, inside etc

Here the right preposition that can be used is "for".

• Usually, the preposition FOR is used to show the purpose of the subject, relationship or the usefulness of the object.
• It can be used to specify the importance of the subject or to put the importance of an event.
• It can be used to denote the duration or time or period to accomplish a task.
• No two prepositions can occur simultaneously because they do not give complete meaning to  the sentence.

Therefore, prepositions are connectors which are used to give a complete meaning to a sentence.