Question

where can you find browser extensions?
in the browser extension store
on random websites
in the browsers toolbar
in the browsers cache

Explanation:

Browser extensions are software add - ons that enhance a web browser's functionality. Browser extension stores (such as the Chrome Web Store for Google Chrome, Firefox Add - ons for Mozilla Firefox) are official and safe places to find and install extensions. Random websites may offer malicious or untested extensions. The browser's toolbar is where installed extensions may appear (but not where you find them to install). The browser's cache is used for storing web page data (not for finding extensions).

Answer:

In the browser extension store.