Why Eilenberg Maclane spaces $K(G,n)$ are $(n-1)$ connected?

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Why Eilenberg Maclane spaces $K(G,n)$ are $(n-1)$ connected? could anyone explain this for me please?

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The usual definitions say that $X$ is an Eilenberg-MacLane space of type $K(G,n)$ if $\pi_n(X)=G$ and $\pi_k(X)=0$ for all other $k$, and a space $X$ is $n$-connected if $\pi_k(X) = 0$ for all $k \leq n$ (for example "$0$-connected" means path-connected, and "$1$-connected" means simply-connected). If $\pi_k(X) = 0$ for all $k\neq n$, then $\pi_k(X)=0$ for all $k\leq n-1$ so it is $(n-1)$-connected.