ans is ( C )

  then not allowed

Hi its answer is  a 1 only

because the condition to check must use == 

1. will always check the condition as true as c=1 is a true condition .

3.is not a syntax of if statement in C

the answer is A & B.
in A dere is a syntax error i.e it should be if(c==1)
and in b u can't use then wid if statement.

the answer is  B i.e 1&3.
in 1. dere is a syntax error i.e it should be if(c==1)
and in 3. u can't use then wid if statement.