In programming, an assignment statement is used to assign a value to a variable or object property. The value on the right side of the assignment statement is typically an expression, which can be a combination of literals, variables, and operators that evaluates to a value.

Option A) A variable - This option is incorrect because a variable is typically on the left side of an assignment statement, indicating where the value will be stored.

Option B) An object property - This option is incorrect because the right side of an assignment statement typically holds the value that will be assigned to the object property.

Option C) An expression - This option is correct because an expression is a valid value that can be assigned to a variable or object property.

Option D) Both a and b - This option is incorrect because a variable is typically on the left side of an assignment statement, indicating where the value will be stored, while an object property is typically on the left side of a property assignment statement.

Option E) All of the above - This option is incorrect because only option C is correct.

The correct answer is option C) an expression.