To verify backend instances for an HTTP(S) load balancer, the health check must target a specific URL (request-path). If the backend requires a specific Host header (e.g., for virtual hosting), the health check must include it. Option B correctly sets both the request-path and the custom Host header, ensuring the backend responds properly. Options A and C involve proxy-header and response parameters, which are not universally required. Option D omits the request-path, which is essential. Thus, B is the correct answer.