(B) Stop words
Stop words occur very frequently in the corpus (e.g., "is", "the", "and") but do not add any meaningful value to it.
The source passage (Test Yourself, Q.7) defines stop words as "words with negligible value that are often removed during preprocessing." They appear frequently but carry no significant meaning, making (B) the correct answer. Text Normalisation and Tokenisation are processes, not word types; "Start words" is not an NLP term.