Final answer:
Intelligent design theory posits the need for an intelligent designer for complex structures but lacks scientific evidence and validation, classifying it as scientifically invalid.
Step-by-step explanation:
The Intelligent Design Theory posits that any complex structure must be the result of an intelligent designer but offers no evidence of this. It does not offer a method by which this can be scientifically tested, therefore it is not considered scientifically valid. So, the correct fill-in-the-blank answer to the student's question would be: Intelligent design theory posits that any complex structure must be the result of an intelligent designer but offers no evidence of this; it does not offer a method by which this can be validated, therefore is not scientific.