C, that is needed选择C,ALL 是主句的主语，is a continuous supply of fuel.是主句的谓语部分。 that is needed是定语从句修饰all，is 是从句里面主语that的谓语。 B 如果改成the thingS needed 也是对的D的意思上不确切。另外，修饰all 的定语从句不能用A。如果用A,全句就是： what is needed is a continuous supply of fuel.就不该有all了。那么what is needed就是主语从句，做is a continuous supply of fuel 的主语。...
