有四根通气管，管径分别为2×100mm，2×75mm，现用汇合通气管将四根通气管汇合在一起伸出屋顶，则汇合通气管所需最小公称直径为（）。
A、DN100B
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重写句子：Attheinternationalmuseum,youcanfindancientEgyptianart.YoucanexploreAfricanartifactsthere.Youcandiscoverbeautifultextilesfromaroundtheworldthere.(parallelstructure)
Ifanearthquakeoccurred，someoftheone-storeyhouses________.
Hewas______towithdrawfromrunningforthepresidency.
Itisdifficultto________theimplicationbetweenthelines.
Beingextremely_____tothecold，Idonotlikeskating.
