Which of the following is an invalid if-else statement?a.if (if (a == 1)){}b.if (a){}c.if ((char) a){}d.if (func1 (a)){}

To determine which of the given if-else statements is invalid, let's analyze each option:

a. if (if (a == 1)){} This statement is invalid because it contains an if statement as the condition of another if statement. In most programming languages, an if statement requires a boolean expression as its condition, not another if statement.

b. if (a){} This statement is valid because it checks the truthiness of the variable "a". As long as "a" is a boolean or can be evaluated as a boolean, this statement is valid.

c. if ((char) a){} This statement is invalid because it tries to cast the variable "a" to a character type within the if condition. In most programming languages, the condition of an if statement should be a boolean expression, not a type casting operation.

d. if (func1 (a)){} This statement is valid as long as "func1" is a valid function that takes "a" as an argument and returns a boolean value. The condition of the if statement should evaluate to a boolean expression.

Therefore, the invalid if-else statement is option a. if (if (a == 1)){}.