Given the task definition and input, reply with output. In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.

Question: When was the type of geometry Hirschfeld published about in 1979 first invented? Passage:In 1979 Hirschfeld published the first of a trilogy on Galois geometry, pegged at a level depending only on "the group theory and linear algebra taught in a first degree course, as well as a little projective geometry, and a very little algebraic geometry." When q is a prime power then there is a finite field GF(q) with q elements called a Galois field. A vector space over GF(q) of n + 1 dimensions produces an n-dimensional Galois geometry PG(n,q) with its subspaces: one-dimensional subspaces are the points of the Galois geometry and two-dimensional subspaces are the lines. Non-singular linear transformations of the vector space provide motions of PG(n,q). The first book (1979) covered PG(1,q) and PG(2,q). The second book addressed PG(3,q) and the third PG(n,q). Chapters are numbered sequentially through the trilogy: 14 in the first book, 15 to 21 in the second, and 22 to 27 in the third. Finite geometry has contributed to coding theory, such as the Goppa code, so the field is supported by computer science. In the preface of the 1991 text Hirschfeld summarizes the status of Galois geometry, mentioning maximum distance separable code, mathematics journals publishing finite geometry, and conferences on combinatorics featuring Galois geometry. Colleague Joseph A. Thas is coauthor of General Galois Geometries on PG(n,q) where n 4.
Links: a. Combinatorics b. Galois geometry c. Coding theory d. Finite field
b