Field costs may include which of the following?

Field costs are associated with the direct expenses incurred during the construction phase of a project, primarily at the job site. These costs can encompass a range of on-site activities and materials required to complete the work.

When considering the options given, expenses related to the project's site are indeed what categorize field costs. This can include expenditures such as labor, materials, equipment rental, utilities specific to the project site, site preparation, and other direct costs that are necessary for executing the project on location.

On the other hand, design office salaries relate to engineering and architectural work that takes place away from the job site, thus not contributing to field costs. Corporate training costs typically address the general training of employees and are not specific to any particular project site or field operations. Similarly, marketing and advertisement expenses are geared toward promoting the business or project at large and have no direct connection to the field costs incurred during construction. Therefore, the option that stands out as correctly identifying field costs is related to expenses specific to the project's site.