Final answer:
The best diagram to depict an alloy of Ni (nickel) and B (boron) is a phase diagram, which shows the different phases of an alloy system at various temperatures and compositions.
Step-by-step explanation:
The question 'Which of the following diagrams best depicts an alloy of Ni and B?' relates to the representation of materials in chemistry. An alloy is a mixture of two or more elements, where at least one of them is a metal, and the mixture has metallic properties. Here, Ni stands for nickel, a metal, and B stands for boron, which can be alloyed with nickel. The best diagram to depict such an alloy would be a phase diagram, as it shows the phase (solid, liquid, or gas) of an alloy system at various temperatures and compositions.
A Venn diagram is used to represent the logical relations between sets, which is not suitable for depicting the composition or phases of an alloy. A scatter plot is used for showing correlations between two variables, which would not show the compositional phases of an alloy effectively. Lastly, a pie chart represents parts of a whole as slices, which wouldn't give the specific phase information for the alloy.
Therefore, the correct answer is A) Phase diagram, as it can represent the temperature and composition phases of the Ni-B alloy system.