\[ \sqrt{\frac{1}{6} \div \frac{1}{6} \div \frac{1}{6} \div \frac{1}{6}}=? \] a) 1 b) 6 c) 25 d) N.A.

Step 1 ：First let's convert each division operation into multiplication by the reciprocal. So, \(\frac{1}{6} \div \frac{1}{6} \div \frac{1}{6} \div \frac{1}{6}\) becomes \(\frac{1}{6} \cdot 6 \cdot 6 \cdot 6\).

Step 2 ：This simplifies to \(\frac{1}{6} \cdot 6 \cdot 6 \cdot 6 = 1 \cdot 1 \cdot 1 \cdot 1 = 1\).

Step 3 ：Now we take the square root of 1, which is also 1. So, \(\sqrt{1} = 1\).

Step 4 ：Therefore, \(\sqrt{\frac{1}{6} \div \frac{1}{6} \div \frac{1}{6} \div \frac{1}{6}} = \boxed{1}\).