What is the term for the space that exists above a drop ceiling or below a raised floor and that isused for air return？（）

A.nowhere （but should be discussed with the customer）
B.on the site survey map and within the site survey text
C.on the customers blueprints
D.in the Cisco WCS Planning Tool

A.Signal strength （4th access point）
B.Signal strength （3rd access point）
C.Channel interference
D.Predictive physical data rate downlink （2nd access point）

A.Crowd of people
B.Office window
C.Metal door
D.Brick wall