The correct definition of a Lightning Web Component property that uses the getAccounts method is option C.
In Salesforce, the @wire decorator is used to read data from one of the wire adapters built into Lightning Web Components or create a JavaScript property in a Lightning web component. The property is then provisioned with data, error, or both. A provisioned property has a specific shape-data and error properties-designed for working with wire services.
In this case, @wire(getAccounts, { searchTern: '$searchTern' }) accountList; is the correct syntax where:
* getAccounts is the Apex method.
* { searchTern: '$searchTern' } are parameters passed to the Apex method.
* accountList is the JavaScript property that gets assigned the data returned by getAccounts.
References: Lightning Web Components Developer Guide