【单选题】Keeping just one node in memory might seem to be an extreme reaction to the problem of memory limitations. Local beam search keeps track of:在内存中仅保存一个节点似乎是对内存限制问题的极端反应。局部束搜索保持：
A: k states rather than just one. k个状态而不仅仅为一
B: m states rather than n states. m个状态而不是n个
C: just one rather than k states. 仅有一个状态而不是k个
D: just m states rather than n states 仅有n状态而不是m