You Might Doubt Whether Your Money Will Actually Reach People

You might doubt whether your money will actually reach people who need it. What does Singer say to this?

A) We should give double to be sure that enough gets through
B) We should go on overseas trips to give our money in person
C) The number he recommends already factors in those uncertainties
D) We also don't know that our money won't get through, so we should keep giving
E) You're obligated to give all you can, whether or not you can be sure of where the money goes