What did Bob fill out before renting the apartment?

The choice of "Form" is appropriate because it indicates that Bob needed to complete a document to proceed with the apartment rental process. Typically, before renting an apartment, prospective tenants are required to fill out a form that gathers essential information, such as personal details, rental history, and employment facts. This form is often the preliminary step in various tenancy processes.

While other options, such as "Application," may seem similar, they may imply a more formalized document that could involve more extensive information or refer specifically to the process of applying for the apartment itself. "Contract" and "Agreement" suggest final, legally binding documents that outline the terms of the lease once the apartment is rented, which occurs after filling out and submitting the initial form. Thus, the choice of "Form" signifies the starting point in the rental application process.