Answer:
a. Sole proprietorships
Step-by-step explanation:
Sole proprietorships are the most common for-profit business type in the United States.
A sole proprietorship is a business entity that has only one owner, and for which, no accounting and legal distinction exist between the business entity and the owner.
This means that the business entity and the owner are taxed under the same terms, and that the owner has unlimited responsability for the sole proprietorship business. For example, in case of bankruptcy, the owner may have to respond to creditors with his own personal wealth.