Triple

Target class: birational invariant (for smooth projective varieties over a field)
Context triple: [Picard group, instanceOf, birational invariant (for smooth projective varieties over a field)]

• A. object in invariant theory
  An object in invariant theory is a mathematical entity, such as a vector space, polynomial ring, or group action, whose structure and symmetries are studied through the functions or quantities that remain unchanged under a specified group of transformations.
• B. cohomological invariant chosen
  A cohomological invariant is a rule that assigns to each object in a given class (such as algebraic varieties, groups, or topological spaces) an element of a cohomology group in a way that is functorial and captures structural or classification information about those objects.
• C. divisor in algebraic geometry
  A divisor in algebraic geometry is a formal finite integer linear combination of irreducible codimension-one subvarieties (or points on a curve), used to encode zeros and poles of rational functions and to study line bundles and linear systems.
• D. algebraic variety
  An algebraic variety is a geometric object defined as the set of common solutions to a system of polynomial equations over a field, studied up to algebraic and topological properties.
• E. problem in invariant theory
  A problem in invariant theory concerns determining and characterizing the algebraic functions (invariants) that remain unchanged under the action of a given group on a vector space or algebraic variety.
• F. None of above.