Coding multiple choices variables

Hello to everyone,
I would like to have some help to code in kobo.
I have a multiple choice variable with the following answers:
a- Owns a house
b- Owns a car
c- Has a television
d- Has running water
e- None of the above
99- Prefer not to answer

Here all answers from “a” to “d” can be selected simultaneously. However, answers “e” and “99” should be selected alone without the possibility of having two answers.
I would like to know if there is a possibility to put codes as validation criteria to control this.

Thanks

Welcome to the community, @Sourou! This post discussed previously should help you solve your issue:

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Thank a lot. It is ok

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