What distinguishes two substances combined to become a compound vs. two substances combined to become a mixture? a. whether they can be easily separated b. whether they chemically bond together c. whether they both are visible d. whether they are heterogeneous

The answer would be B.

Why?

Because compounds are a combination of two or more elements, while a mixture can be virtually anything. We cannot simply mix hydroxide and sodium together and claim it as a physical bond, it doesn't make sense since they react with each other in some way. However, mixtures are typically physical, since a chemical change most likely would not occur if we mixed popcorn and pretzels together in a bowl to make chex mix.

I hope I could help and I hope this made sense!

What are the options? i can you if you give them.