Answer: b. stainless steel.
Step-by-step explanation:
Heterogeneous mixtures : It is a mixture that has non-uniform composition throughout the solution and the particle size or shapes are also different. There is a physical boundary between the dispersed phase and dispersion medium.
Homogeneous mixtures : It is a mixture that has uniform composition throughout the solution and the particle size or shapes are not different. There is no physical boundary between the dispersed phase and dispersion medium.
1. Noodle soup is heterogeneous as the components are physically distinct.
2. Stainless steel is homogeneous as the components are not physically distinct.
3. Oxygen is an element.
4. Distilled water is a compound as it is free of other materials and ions.