A water tank currently holds 4,000 milliliters of water. If the maximum capacity of the tank is 0.008 kiloliters, what percentage of the tank's total capacity remains unfilled?

The correct option is 50%.

To find the percentage of the tank's total capacity that remains unfilled, we need to compare the volume of water currently in the tank to the total capacity of the tank in the same unit of measurement.

Step 1: Convert the total capacity into milliliters (mL).
We are given that 1 kiloliter (kL) = 1,000 liters (L) and 1 liter (L) = 1,000 milliliters (mL).
Therefore, 1 kL = 1,000 × 1,000 mL = 1,000,000 mL.

Now, convert 0.008 kiloliters to milliliters:

$\text{Total Capacity}=0.008\times \mathrm{1,000,000}\text{mL}=\mathrm{8,000}\text{mL}$

Step 2: Calculate the unfilled capacity.
The tank currently holds 4,000 mL of water out of a total capacity of 8,000 mL.

$\text{Unfilled Capacity}=\text{Total Capacity}-\text{Current Water Volume}$

$\text{Unfilled Capacity}=\mathrm{8,000}\text{mL}-\mathrm{4,000}\text{mL}=\mathrm{4,000}\text{mL}$

Step 3: Calculate the unfilled percentage.
Now, find the percentage of the unfilled capacity relative to the total capacity:

$\text{Unfilled Percentage}=\left(\frac{\text{Unfilled Capacity}}{\text{Total Capacity}}\right)\times 100\text{\%}$

$\text{Unfilled Percentage}=\left(\frac{\mathrm{4,000}}{\mathrm{8,000}}\right)\times 100\text{\%}=0.5\times 100\text{\%}=50\text{\%}$

Thus, 50% of the tank's total capacity remains unfilled.