Answer: a) Sales
Step-by-step explanation:
Fulfillment is defined as the mechanism in which orders are received, made ready and then delivered to the consumer. Execution of order from preparing stage to shipping to customer is done through fulfillment.
Sales department of organization is the section that holds the process of receiving orders from customer, preparing the good or product and sending it to recipient.
Other options are incorrect because accounting department,warehouse department and purchasing section are not the fulfillment department/block of any organization .Thus, the correct option is option(a).