That is the first explanation of the first question and there is written about an argument list ( it is bold in the quoted test ), but what actually is meant is parameter list, because:Syntactically, this lambda expression is correct. However, remember that a lambda expression does not create a new scope for variables. Therefore, you cannot reuse the variable names that have already been used to define new variables in your argument list .
Here, observe that the variable d is already defined so your argument list cannot use d as a variable name. It would be like defining the same variable twice in the same scope.
An argument list is a list of arguments, when you define for example a method.
A parameter list is a list of paramters and you call with a parameter list something like for example a method, but it has to fit with the argument list of the calles method.
So there is a difference between argument and parameter. ( This difference is for me very important, but I do not know how for you ).
There is a another thing about it. I would say it could be seen as correct, because you "define" the argument list for the method, which is later called ( it is a lambda expression ), but I would like it if you would add something to your explanation to make it more clear.