Which of the following describes a graph in terms of data structures?

A graph is defined as a collection of nodes (often referred to as vertices) connected by edges. Unlike other data structures, such as trees which have a strict hierarchical relationship between nodes, graphs allow for connections between nodes that do not follow a specific order or hierarchy. This means that any node can be connected to any other node, creating a more flexible and complex structure.

In the context of data structures, this characteristic of being interconnected without a strict hierarchy is what sets graphs apart. They can represent various real-world relationships and structures, such as social networks, transportation systems, and more.

The other choices describe different data structures: one mentions a hierarchical connection which is more aligned with trees, another describes a linear sequence which resembles arrays or linked lists, and the last option refers to collections of elements stored in contiguous memory, akin to arrays. These descriptions do not capture the unique qualities of graphs, making the option describing nodes connected by edges without a strict hierarchy the most accurate representation of a graph.