A filled torus (a doughnut) is a 3-manifold homeomorphic to \(S^1 \times D^2\), where \(D^2\) is the 2-dimensional disk. There exists a deformation retract from the doughnut to a circle, so the fundamental group of the doughnut is \(\pi_1(S^1 \times D^2) \cong \mathbb{Z}\).
NYT Pips hints, answers for March 6, 2026，详情可参考PDF资料
，详情可参考雷电模拟器官方版本下载
Иран ударил по зданию Минобороны Израиля и аэропорту Бен-Гурион02:19
PEP 692 “Using TypedDict for more precise **kwargs typing”，详情可参考体育直播
前两篇报告分别剖析了 2025 年中国消费市场的韧性底色与多元生态，揭示了 50.1 万亿元消费大盘的增长逻辑与结构特征。