hello
to solve this question, let's simply draw the tile to give an illustration of it
we can solve this question by simply using pythagorean theorem
from pythagorean theorem,
[tex]\begin{gathered} x^2=y^2+z^2 \\ y=z=7\sqrt[]{5} \end{gathered}[/tex][tex]\begin{gathered} x^2=y^2+z^2 \\ x^2=(7\sqrt[]{5})^2+(7\sqrt[]{5})^2 \\ x^2=490 \\ \text{take square root of both sides} \\ x=\sqrt[]{490} \\ x=7\sqrt[]{10} \end{gathered}[/tex]
from the calculation above the value of the diagonal is option C
