根据情景内容，在空白处填入合适的单词。
A: Well, Mike, nowadays there’s much talk (1)______
nanometer. But what on (2)_______ is it?
B: Nanometer is a (3)_______ scale. It’s one billionth of a meter, roughly ten times the size of an individual atom.
A: Hmm...it’s (4)________ to figure out the exact size, I’m afraid.
B: Well, let’s make it this way. For comparison, 10 NM is 1000 times (5)________than the diameter of a human hair. There are as many nanometers in an inch as there are inches in 400 miles.
A: I see. Thank you.