Many difficulties have as a result of the changeover to a new type of fuel.
A. risen
B. arisen
C. raised
D. arose
网友回答
A. risen
(答案→)B. arisen
C. raised
D. arose
解析：句意：由于改变了成一种新型的燃料，许多困难出现了。Rise上升；arise出现；raise提高；arose是arise的过去式，arisen是过去分词；因为前面有have，所以后面应该用过去分词，根据句意故选B。