I need help I just don't know

Which of the fallowing best completes the sequence 12,8,5, a) 1 b) 2 c)4 d)0

Which expression gives the area of the triangle shown below

A3-dimensional figure has a square base and 4 lateral faces that meet at a point. explain the difference between the cross sections when a slice is made perpendicular to the base through the vertex, and when a slice is made perpendicular to the base and not through the vertex