Which type of partnership involves personal liability for all partners?

In a general partnership, all partners share personal liability for the debts and obligations of the partnership. This means that if the partnership incurs debt or faces a lawsuit, each partner's personal assets can be at risk to satisfy those obligations. The fundamental characteristic of a general partnership is that it allows for a shared management structure and equal responsibility among partners in terms of liability.

In contrast, a limited liability partnership (LLP) provides some protection to its partners from personal liability for certain actions of the partnership, particularly in professional contexts, such as law firms or accounting firms. A professional partnership is similar to a general partnership but is often used specifically for licensed professionals who may want to operate together while also following specific regulations related to their profession. A partnership at will simply refers to a partnership that can be dissolved by any partner at any time without cause, and does not inherently relate to personal liability.

Thus, the defining characteristic of a general partnership is the personal liability of all partners, making it the correct choice in this context.