单选题 Let’s be the set of all positive integers having at most 4 digits and such that each of the digits is 0 or 1．What is the greatest prime factor of the sum of all the numbers in S?

A、 11
B、 19
C、 37
D、 59
E、 101

【正确答案】 E

【答案解析】By writing down all the positive integers in S, their sum can be found.