What valid expression can be used to so that HTTP configuration can pick the value from configuration file?

Refer to the exhibits.

Mule application has an HTTP request configuration where host name is hardcoded. Organization is looking to move host and port values to configuration file.

What valid expression can be used to so that HTTP configuration can pick the value from configuration file?
A . #[training.host]
B. ${http.host}
C. #{training.host}
D. ${training.host}

Answer: D

Explanation:

Correct answer is ${training.host}