單項(xiàng)選擇題

建筑物的經(jīng)過年數(shù)有實(shí)際經(jīng)過年數(shù)和有效經(jīng)過年數(shù)，它們之間關(guān)系為（）.

A.有效經(jīng)過年數(shù)等于實(shí)際經(jīng)過年數(shù)
B.有效經(jīng)過年數(shù)短于實(shí)際經(jīng)過年數(shù)
C.有效經(jīng)過年數(shù)長(zhǎng)于實(shí)際經(jīng)過年數(shù)
D.有效經(jīng)過年數(shù)可能長(zhǎng)于或短于實(shí)際經(jīng)過年數(shù)

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