What is the slant height in a rectangular or square pyramid?

a. the height of the pyramid from the apex straight down to the middle base of the pyramid
b. an edge of an triangular face
c. the height from the apex straight down to the base of the triangular face where it forms a right angle.
d. the distance across the triangular face

c. the height from the apex straight down to the base of the triangular face where it forms a right angle.