challenge: What is the primary characteristic of the Symmetric Rank 1 (SR1) method?
  
  A. It guarantees a positive definite update of the Hessian matrix
  B. It is a quasi-Newton method that updates the Hessian based on gradients at two points
  C. It is a secant method for a single-dimensional problem
  D. It breaks the symmetry of the matrix
  Answer: 