Carens Accepts That It Is Possible for the Sudden Opening

Carens accepts that it is possible for the sudden opening of one country's borders to do more harm than good from a liberal egalitarian perspective. However, he argues that

A) in practice, feasible policy options will not entail major costs to current citizens.
B) liberal egalitarianism is false, and so this possibility is irrelevant.
C) sometimes you have to do more harm than good in the short term to do more good in the long term.
D) all of the above