Whether a complete non-compact non-flat Riemannian $n$-manifold $M$ with non-negative sectional curvature has Euclidean volume growth?
That is, whether there is a constant $C>0$ such that $\mathrm{Vol}(B_x(r))\geq Cr^n$ for all $r>0$ and $x\in M$? Here $\mathrm{Vol}(B_x(r))$ is the volume of the $r$-ball in $M$.
Since manifolds with non-negative Ricci curvature and Euclidean volume growth are studied a lot, I am curious about the non-negative sectional curvature case.