问题补充：
Josephs car has a flat tire now is to walk to the nearest telephone.2.Josephs car has a flat tire now is to walk to the nearest telephone.A.He can doB.He can do thatC.All he can doD.That he can do选择
答案：
C.All he can do 表示他现在所能做的就只有走进最近的电话亭 主语从句 谓语是 is ,
A和B都不完整 填进去还是没有主语 D That 不能再句首引导主语从句.
======以下答案可供参考======
供参考答案1:
选C。后半句是个省略了that的定语从句，还原后为…all that he can do now is…，其中，all是的主语，同时也是定语从句的先行词，that是连接词（在原句中已省略）is后面的是表语。
供参考答案2:
主语从句。。is前面。主语是 all he can do
