第4题: [单项选择]To a highly imaginative writer, ______ is a pad of paper and a pen. A. all are required B. all required is C. all is required D. all that is required 参考答案:D 答案解析:根据空当后内容可推断,空当部分为主语。A和C为主谓结构,不能充当主语。B中多了动词is,因此,也可排除。D可充当主语,all后为that引导的定语从句,因此D为正确选择。