What are the rules for naming variables in programming? The first character must be a letter If there is more than one character, only letters or n...

What are the rules for naming variables in programming?
The first character must be a letter
If there is more than one character, only letters or numbers can be used
Variable names written in uppercase letters are different from lowercase letters
No reserved word can be used as a variable name

a) The first character must be a letter
b) If there is more than one character, only letters or numbers can be used
c) Variable names written in uppercase letters are different from lowercase letters
d) No reserved word can be used as a variable name
e) All of the above