Final answer:
The online installation of an extension typically requires the user to download the extension file, quit the browser, install the file, and then restart the computer.
Step-by-step explanation:
The best description of online installation of an extension is option b. The user downloads the extension file, quits the browser and installs the file, and then must restart the computer in order for the installation to take effect. Restarting the computer is necessary to ensure that the extension is properly integrated into the browser and can function correctly.
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