The correct term for a class of all possible subsets of a space is not "universal set," but rather:

B. alpha-field (or more commonly, σ-field or sigma-field in probability theory).

A sigma-field (or sigma-algebra) is a collection of subsets of a given space that includes the space itself, is closed under complementation, and is closed under countable unions. This concept is fundamental in measure theory and probability.

Here's a brief overview of the terms:

- Universal Set: This refers to the set that contains all objects under consideration, usually denoted as \( U \) in set theory.
- Alpha-field (σ-field or Sigma-field): A collection of subsets that is closed under complementation and countable unions. This is used in measure theory.
- Sample Space: The set of all possible outcomes of a probabilistic experiment.
- Probability Space: A mathematical construct that provides a formal model for a probability experiment, consisting of a sample space, a sigma-field of events, and a probability measure.
- Random Space: This is not a standard term in probability theory.

So the correct answer should be B. alpha-field (or sigma-field).