[A] upon [B] back [C] off [D] away

参考答案:

A本题考查短语动词辨析。空格处填入的介词或副词与call构成短语动词，接sb. to do sth.作复合宾语。符合要求的是［A］，call upon sb. to do sth.意为“请求/要求某人做某事”，如：We call on every friend to support the plan.（我们请求每一位朋友支持这项计划。）call back意为“回电话；叫（某人）回去”，如：She was about to leave when her secretary called her back.（