Where do you define the class that provides options for the select field that enables or disables the provider in the file etc/adminhtml/system.xml?

A Magento industry partner shipping provider has tasked you to build their integration module called MyCompany_ShippingProvider.

A. <option_model>MagentoConfigModelConfigOptionYesno</option_model>
B. <source_model>MagentoConfigModelConfigSourceYesno</source_model>
C. <frontend_model>MagentoConfigModelConfigFrontendYesno</frontend_model>
D. <backend_model>MagentoConfigModelConfigBackendYesno</backend_model>