To write in a casual voice, it would be to avoid

everyday language.
technical language.
common abbreviations.
a first-person perspective.

B: technical language

Explanation:

To write in a casual voice, one can use everyday language, common abbreviations, and a first-person perspective. But it would be helpful to avoid a technical language because this type of language, besides being formal, it is used for a specific subject, with appropriate terminology that only specialized people in that field would understand.

what are you asking? this is gibberish.