Directions: In the sentence given below, four words have been highlighted. Identify the correct sequence of the words in the sentence. Also, one of the highlighted words does not fit the context of the sentence and will need to be replaced. Identify the correct sequence and replacement and mark that as your answer.

Several niche (A) have rivals (B) but most are emerged (C) platforms without the capacity to grow at the necessary scale to substantiate (D) Twitter.