Final answer:
Add the Lazysizes script in the theme.liquid file before the closing tag of a Shopify theme for optimal performance.
Step-by-step explanation:
When integrating Lazysizes, a popular lazy loading library, into a Shopify theme, the appropriate place to add the script is usually within the theme.liquid file. Specifically, you should place the script before the closing </body> tag to ensure it loads after the main content of the page. This approach allows for the rest of the page to render quickly while images or iframes designated to be lazily loaded are deferred until they are needed.
The correct answer to the question is:
B) theme.liquid > before the closing </body> tag