Step 1: Understanding the sequence of execution.
In a typical web application, the sequence begins when the HTTP request is made. The server processes this request, executes the necessary program to generate the response, and then returns an HTTP response.
Step 2: Evaluate the sequence.
- (B) Calls an application in response to the HTTP request: This is the first step when a server responds to an incoming request.
- (A) HTTP Request: This is the request initiated by the client (browser).
- (C) Program executes and produces HTML output: After the HTTP request, the server processes the program to produce HTML content.
- (D) HTTP Response: Finally, the server sends back an HTTP response containing the HTML content.
Step 3: Conclusion.
The correct sequence of execution is:
(B) Calls an application → (A) HTTP Request → (C) Program executes → (D) HTTP Response.
Final Answer:
\[
\boxed{\text{The correct sequence is (B), (A), (C), (D).}}
\]