From section F: 'If you have a flu, do you go to x bed or you continue your x study as well?' 'Flu' is a general illness, so 'a'. 'Bed' and 'study' are used in a general sense (go to bed, continue study), so no article.
Class 6 › English Grammar and Composition › Chapter 3: Articles: a, an, the › Topic: Introduction to articles: a, an, the
Aligned to the NCTB national curriculum.