(a) Helps in classifying the type and genre of a document.
Text Classification (document classification) classifies a sentence or document category-wise into predefined groups or categories.
The source passage under Applications of NLP describes Text Classification as a tool that "classifies a sentence or document category-wise" into predefined groups — i.e., it classifies the type and genre of a document. The other options describe unrelated NLP tasks (corpus display, document creation, word inclusion), so (a) is the only correct answer.