________ difficulties they may come across, they will help one another to get over them．

A.However

B.Whatever

C.Whichever

D.Since

答案及解析： B

wh-ever引导从句时经常是名词性从句或让步状语从句，根据句意本句引导让步状语从句。whatever修饰名词，however修饰形容词或副词。故选择B项。