A、By thE BuilDing mEthoD through whiCh thE BuilDErs wAnt to sAvE EnErgy.
B、By thE limit oF thE Flow oF Air BEtwEEn insiDE AnD outsiDE.
C．By thE BuilDing things whiCh ArE mADE oF mAn-mADE mAtEriAls.
D．not only By thE limit oF Air -Flow But Also By thE mAn-mADE mAtEriAls.