Determine which of the following words can be formed using each letter of the given word "POTASSIUM" only once.

Let's evaluate the letter frequencies available in $\text{POTASSIUM}=\{\text{P:1, O:1, T:1, A:1, S:2, I:1, U:1, M:1}\}$.
* Option A (MASS): Requires $\text{M}\times 1,\text{A}\times 1,\text{S}\times 2$. All are available. Thus, it can be formed.
* Option B (TOAST): Requires two $\text{T}$ 's, but we only have one.
* Option C (MOUSE): Requires an $\text{E}$, which is absent.
* Option D (POPPS): Requires three $\text{P}$ 's, but we only have one.