Answer:
C. Paragraph.
Step-by-step explanation:
Business letters are a form of communication where the use of formality is of the utmost requirement. And in writing these business letters, paragraphs are used. Flowcharts, diagrams and even if-then tables are not something that can be included or used for business letters. Letters of business importance should always be written in paragraph form, describing the details or issues in perfect form. Also, the inclusion of the details of the sender and also the following of formal form of addressing the receiver is mandatory.