The correct answer is (b) Two dimensional
For explanation I would say: Matrices are like strictly typed two-dimensional arrays. You create a matrix using the matrix function, which accepts five parameters: a vector to use as the content, the number of rows to shape the content into, the number of columns to shape the content into, an optional boolean value to indicate whether the content should be shaped by row or by column (the default is FALSE for by column), and a list that contains vectors for row names and column names:
matrix([content vector], nrow=[number of rows], ncol=[number of columns], byrow=[how to sort], dimnames=[vector of row names, vector of column names]).
