c. $6 \times 10^{-7}=\square=$ (Type an integer or a decimal.)

Step 1 ：The question is asking for the decimal representation of the scientific notation $6 \times 10^{-7}$.

Step 2 ：In scientific notation, the number $a \times 10^{b}$ represents the number $a$ shifted $b$ places to the right (if $b$ is positive) or to the left (if $b$ is negative) of the decimal point.

Step 3 ：So, $6 \times 10^{-7}$ represents the number 6 shifted 7 places to the left of the decimal point.

Step 4 ：The decimal representation of $6 \times 10^{-7}$ is \(\boxed{0.0000006}\).