A linear function has this form:
[tex]y=ax+b[/tex]Notice that option A cannot be written in this form, because x and y have a square power. If you clear y you'll get:
[tex]y=\sqrt[]{1-x^2}[/tex]Option B you can write it in the form of a linear equation:
[tex]y=14-x[/tex]For this option, a = -1 and b = 14
Option C cannot be written in this form:
[tex]y=\frac{6}{x}[/tex]And option D can be written like that:
[tex]y=6x+3[/tex]Here, a=6 and b=3.
So, options B and D are linear equations