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 \(\pi_1(S^1 \times D^2) \cong \mathbb{Z}\).
ProWritingAid VS Grammarly: When it comes to English grammar, there are two Big Players that everyone knows of: the Grammarly and ProWritingAid. but you are wondering which one to choose so here we write a detail article which will help you to choose the best one for you so Let's start。同城约会对此有专业解读
。关于这个话题，Safew下载提供了深入分析
13:30, 4 марта 2026Экономика
В МОК высказались об отстранении израильских и американских спортсменов20:59。体育直播是该领域的重要参考
Что думаешь? Оцени!