Karl, Lim, Mary and Navin are each competing in a different sporting event at the Olympic Games - basketball, swimming, taekwondo and women\textquotesingle s rhythmic gymnastics. Karl and Navin do not know how to swim. Mary is the only female. Karl\textquotesingle s event does not require a ball. Which event is Navin competing in? 
Overseas Competition->Knowledge Point->Counting Modules->Permutations and Combinations->Combinations
Since \textbf{Mary} is the only female, she must have participated in the women\textquotesingle s\textbf{~Rhythmic gymnastics} as the rest are males.  Since Karl and Navin do not know how to swim, \textbf{Lim} is the only male left and thus he participated in the S\textbf{wimming} event.  And since \textbf{Karl}\textquotesingle s event does not require a ball, he must have participated in \textbf{Taekwondo}.  We can thus conclude that \textbf{Navin}~participated in \textbf{Basketball}. 