Write an inquisitive question about a specific text span in a given sentence such that the answer is not in the text.

Let me give you an example: Sentence: The Obama administration is developing additional screening protocols for airline passengers both overseas and in the United States to control infectious diseases such as Ebola, President Barack Obama said Monday .<sep>Span: Obama administration
The answer to this example can be: What was the duration of the Obama administration?
Here is why: It is an inquisitive question based on the specific span of the sentence.

OK. solve this:
Sentence: Investigators have used ground - penetrating radar and specialized GPS devices to peek below the landscape , but no one is entirely certain why the holes form along the surface of this landmark , which attracts thousands of visitors each year .<sep>Span: GPS devices
Answer:
Is this different from the GPS devices we use on a daily basis?