Data type MCQ 4 : Valid Identifier or Variable name in C

In C Programming (Multiple Choice Question 4 ) Which Identifier is invalid ?

1. int
2. _sum
3. 1sum
4. s_num1
5. s num1
6. s-num1

Options :

  1. Options : 1,2,5
  2. Options : 1,3,5,6
  3. Options : 1,2,5,6
  4. Options : 3,4,5,6


Why & How ?
Rules for Valid Identifier

  1. First Letter Should be “Underscore” or “Alphabet”
  2. Digits are allowed except first Place
  3. Special Characters are not allowed
  4. White spaces not allowed