Which of the following represents the inverse of the matrix below?

To find an inverse matrix you first have to find the determinant and then put the absolute value of it under a 1.  That's what is sitting outside in front of all those matrices.  What you have to do now is multiply that determinant by what I teach to my students as the "mixed up matrix".  They always remember from that.  Change the position of the terms on the major axis (here they are a and d), and then switch the signs on the other 2 terms.  Our inverse matrix then is