Question

which of the following is a homogeneous mixture?
salt dissolved in water
a sample of pure copper
milk
oatmeal with berries

Explanation:

A homogeneous mixture has a uniform composition throughout. Salt dissolved in water forms a solution where salt is evenly distributed. Pure copper is a pure substance (element), not a mixture. Milk is a colloid (not a true homogeneous mixture at molecular level in strict sense as it has tiny fat globules etc. dispersed). Oatmeal with berries is a heterogeneous mixture as components are not uniformly distributed.

Answer:

Salt dissolved in water