What are the modifiers used to modify S, V and SC? 

  a. The subject in a sentence is always a noun,  a noun phrase or

      a noun clause.

     In English, adjectives, adjective phrases and adjective clauses are

     used to modify the subjects.

 b. The verb in a sentence can be a single verb or a verb phrase.

     They will be modified by adverbs, adverb phrases and adverb

      clauses.

 c. The subject complement in a sentence can be a noun or an

      adjective.

     When it is a noun, it is modified by adjectives. When it is an

     adjective, it is modified by adverbs.      

     For example:  He looks very cool. (adverb)