What are the values contained in the two character shell variables: $$0,$ $$1,$ $$2,...$ $$9$

Group of answer choices

$$0$ has no value and $$1$ to $$9$ have arguments of the command

$$0$ is not a valid shell variable and variables $$1$ to $$9$ have arguments of the command

None of them are valid shell variables

$$0$ has the command $($first word$)$ and variable $$1$ to $$9$ have arguments of the command command

test command is to evaluate an expression and $[]$ is the short form for test command