The External Skin of the Reliance Building in Chicago Consists

The external skin of the Reliance Building in Chicago consists of:

A) a glazed cast-iron-grid attached to steel columns and beams.
B) cast-concrete panels infilled with glass and bolted to an iron frame.
C) glass and stone supporting themselves, with floors supported by steel columns.
D) glass and terracotta clipped onto an internal steel skeleton.
E) None of the answers is correct.