Your ad can show to a potential customers when your targeted language matches:

Your ad can show to a potential customers when your targeted language matches:

• the customer’s browser setting
• the customer’s Google interface language setting
• the customer’s operating system language
• the language of websites a user visits most often

Correct Answer is:

• the customer’s Google interface language setting

Explanation: Your ad can show to a potential customers when your targeted language matches the customer’s Google interface language setting. Language is targeted on the basis of potential customer’s Google interface language setting.

Read more here: https://wpexpertguides.com/adwords-fundamental/your-ad-can-show-to-a-user-when-your-targeted-language-matches/