None of the choices is a suitable fill-in for the blank.
The question is fishing for "solution", but that makes
the statement false and misleading.
Salad dressing is a well-blended mixture.
Blood is a well-blended mixture.
Milk is a well-blended mixture.
Petroleum is a well-blended mixture.
None of these substances is a solution.
A solution is not a well-blended mixture.