Answer:
The correct answer of the given question is option(A) i.e salesTax
Step-by-step explanation:
Variable are the storage area which value varies during the execution of aprogram .
some of the rules of variable are
1 Variable always start with alphabet.
2 We cannot give variable name any reserve keyword.
3 Variable cannot start with digit.
4 We cannot use special symbol like -,$ to declare any variable
In option (b ) input-string ,it is invalid variable because it uses special symbol "-" to declared the variable.
In option (c) 25Percent , it is invalid variable because it violate the rule of variable and start with digit.variable cannot start with digit
In option( d )double, it is invalid variable because it violate the rule of variable because double is keyword and variable never be a keyword.
So option(A) is correct it follow the rule of variable.