Final answer:
Multiple lines of evidence including geological features, mineral formations, and chemical analysis of Martian samples substantiate the presence of past water on Mars, confirming that option d, 'All of these are evidence for past water on Mars,' is correct.
Step-by-step explanation:
Evidence for past water on Mars includes a variety of geological and chemical indicators discovered over years of exploration with various rovers and orbiters. Specifically, the evidence includes: branching channels in the shape of riverbeds captured by orbiting spacecraft, round hematite deposits nicknamed 'blueberries' found by the Opportunity rover, and a conglomerate rock that appears to have been created in streams uncovered by the Curiosity rover.
Analysis of Martian samples indicates the presence of both water and organic compounds, suggesting that liquid water and perhaps even oceans existed on Mars, which might have harbored life. Moreover, certain minerals such as hematite require watery environments to form, and the presence of these minerals gives further credence to the hypothesis of past water on Mars.
Thus, the correct answer is: d. All of these are evidence for past water on Mars.