To apply the product rule of exponents, we can use the property that states \( a^m \times a^n = a^{m+n} \).
In this case, we have:
\[ 1^6 \times 1^2 \times 1^1 \]
Applying the product rule:
\[ 1^{6+2+1} = 1^{9} \]
So the equivalent expression is \( 1^9 \).
Thus, the correct answer is:
a) \( 1^{9} \).