In a Single- Span Mullion System for a Glass Curtain

In a single- span mullion system for a glass curtain wall,

A) two expansion anchors are provided at every alternate floor level.
B) one expansion anchor is provided at every alternate floor level.
C) only one expansion anchor is provided for the entire height of the wall.
D) one expansion anchor is provided at every floor level.
E) two expansion anchors are provided at every floor level.