Global holomorphic sections of the complex tautological line bundle vanish ($H^0({\mathbb{CP}}^n,\mathcal{O}(-1))=0(n\ge 1)$)

The complex tautological line bundle is a holomorphic subbundle of the trivial bundle with fibre ${\mathbb{C}}^{n+1}$. A global holomorphic section therefore gives $n+1$ global holomorphic functions on compact connected Complex projective space. The maximum modulus principle makes them constant. The constant vector must lie in every projective line through the origin, whose intersection is zero for $n\ge 1$. For $n=0$, the base is one point and the section space is instead $\mathbb{C}$.