Which command is used to run a Node.js application?run app.jsstart app.jsnode app.jsnpm app.js

To run a Node.js application, the correct command is node app.js.

Explanation:

1. node: This is the command used to invoke the Node.js runtime.
2. app.js: This is the name of the JavaScript file that contains your Node.js application code.

When you execute node app.js in the command line, the Node.js runtime will start executing the script defined in app.js.

The other options listed:

• run app.js and start app.js are not valid commands for running a Node.js application.
• npm app.js suggests using npm (Node Package Manager), but without the command like npm start, it does not run the JavaScript file directly.

Final Answer

The command to run a Node.js application is: node app.js.