Question

Which of the following is not valid identifier?

  (a) a_
  (b) _a
  (c) 1a
  (d) _1​

Answer 1

Answer:

c.1a

this is the ans i hope

Answer 2

The not valid identifier is $1a$

Explanation:

• Only alphanumeric characters (a-z, A-Z, 0-9) (i.e. letters and numerals) and the underscore(_) sign are allowed in an identification.
• The names of the identifiers must be unique.
• An alphabet or underscore must be the first character.
• Keywords cannot be used as identifiers.
• The first thirty-one ($31$) characters are the most important.
• It can't have any white spaces in it.
• Case matters when it comes to identifiers.