sin^2t + cos^2t = 1
sint = 1/4
(1/4)^2 + cos^2 t = 1
1/16 + cos^2 t = 1
cos^2 t = 1 - 1/16
cos^2 t = (16 - 1)/16
cos^2 t = 15/16
take root both side,
[tex]\begin{gathered} cost=\sqrt[]{\frac{15}{16}} \\ \cos t=\frac{\sqrt[]{15}}{4} \end{gathered}[/tex]
so the answer is option D
