To answer this question, the user needs to know what WML stands for and what types of browsers can display WML pages.

WML stands for Wireless Markup Language, a markup language used for creating content for mobile devices.

Now, let's go through each option and explain why it is right or wrong:

A. WAP: This option is partially correct. WAP (Wireless Application Protocol) is a technical standard for accessing information over a mobile wireless network. WML is the markup language used to create content for WAP-enabled devices. Therefore, WML pages can be displayed in a WAP-enabled browser.

B. Web: This option is incorrect. WML pages are not designed for display in a standard web browser. Instead, they are designed for display on mobile devices.

C. Mobile: This option is partially correct. WML pages are designed for display on mobile devices and can be displayed in a browser on a mobile device.

D. All: This option is incorrect. WML pages are not designed for display in a standard web browser, so they cannot be displayed on all types of browsers.

Therefore, the answer is: A. WAP