下面關(guān)于m階B樹(shù)說(shuō)法正確的是()
①每個(gè)結(jié)點(diǎn)至少有兩棵非空子樹(shù);
②樹(shù)中每個(gè)結(jié)點(diǎn)至多有m一1個(gè)關(guān)鍵字;
③所有葉子在同一層上;
④當(dāng)插入一個(gè)數(shù)據(jù)項(xiàng)引起B(yǎng)樹(shù)結(jié)點(diǎn)分裂后,樹(shù)長(zhǎng)高一層。
A.①②③
B.②③
C.②③④
D.③