单选题 ______ your help, they"d never have been able to overcome the difficulties.
【正确答案】 C
【答案解析】若虚拟条件句中含有were，had或should等时，连词if可以省略，并使用倒装语序。were it not若不是…的话，若非。had it not been for如果不是因…。