Take $X$ a hypersurface in $\mathbb{C}P^{n+1}$ of degree $d$, denote $\Lambda_X=H^n(X,\mathbb{Z})$. We know that $\Lambda_X$ is a finitely generated Abelian group. I was wondering whether $\Lambda_X$ is always free (for any $n$, $d$). Anyone know an answer or a refrence about this? Thanks a lot!