The phrase "K-1 Fianc?Visa" can be expressed by fingerspelling "K" "1" and then signing "fianc? (fianc?) and then fingerspelling "visa" (V-I-S-A).
See:
K
The purpose of this page isn't to discuss the meaning of a K-1 Fianc?Visa but rather to simply discuss how to sign the phrase.
As a form of clarification when you are about to sign "K-1 Fianc? Visa" you might (upon first reference or usage) want to use the QUOTE sign just before doing the phrase and then using the QUOTE sign a second time to finish your quote.
Notes: