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Multiple choice

In partial-wave analysis of scattering from a central potential, what happens at LOW energy (k*a << 1, where a is the potential range), and why?

Only very high ell channels survive, because low-energy particles carry large angular momentum
All partial waves up to ell = infinity contribute equally, because angular momentum is unbounded
Only the ell = 0 (s-wave) channel survives, because a particle with momentum hbar*k feeling a potential of range a carries appreciable angular momentum only up to ell_max ~ k*a
Scattering vanishes entirely, because no partial wave is shifted at low energy