purchases account is classified as:

a. an expense account
b. an asset account
d. a cost account

To determine the classification of a purchases account, we need to understand the nature of the transactions recorded in that account.

A purchases account is typically used to record the cost of goods or services acquired by a business for the purpose of reselling them to customers. Therefore, based on this information, the correct classification for a purchases account is:

b. An asset account

Explanation:
In accounting, assets are economic resources owned or controlled by a business entity. Assets are expected to provide future benefit to the company. Purchases of goods or services are considered an investment in inventory, which is an asset for a business. As the purchases account represents the cost associated with acquiring inventory, it is classified as an asset account.

Expense accounts, on the other hand, are used to record costs directly related to the operation of a business, such as rent, salaries, utilities, etc. Cost accounts, which are also known as cost of goods sold accounts, are used to track the costs directly associated with the production or acquisition of goods or services sold by a business.

It is important to note that accounting classifications can vary based on the accounting framework being used and the specific nuances of a company's industry or operations. However, in general, a purchases account is classified as an asset account.