{{i}}{{B}} quEstions 17 to 20 ArE BAsED on thE Following monologuE ABout EnErgy ConsErvAtion. you now hAvE 20 .sEConDs to rEAD quEstions 17 to 20.{{/i}}{{/B}}

whAt is thE mAin topiC oF this lECturEA．BiCyClEs AnD CArs.
BuilDing CoDEs.
C．EnErgy ConsErvAtion.
D．nEw housing ConstruCtion.