Final answer:
In the given context, 'd: a heterogeneous mixture' refers to a non-uniform mixture comprising physically combined, distinct substances, unlike a homogeneous mixture where the composition is uniform.
Step-by-step explanation:
In the context of this question, 'd: a heterogeneous mixture' signifies a type of mixture that is non-uniform in its composition. This means it comprises two or more substances physically combined, but not chemically, and these substances can be visibly distinguished. For instance, a salad is a heterogeneous mixture because you can physically separate the lettuce, tomatoes, onions, and other ingredients. This contrasts with a homogeneous mixture that is uniform in its composition, such as sugar dissolved in water where its components can't be physically separated.
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