The correct way of layout declaration?

Question

I'm doing some Magento 2 certification test questions. There's one question I do not understand.

The question is as the screenshot. My answer is D, but the correct answer from the test is B

I've been working a lot with layout xml, and I'm quite convinced D is the correct way to declare a custom layout. But if B is the correct answer, can anyone explain why?

Answer 1

The node attributes are ordered alphabetically

This is the clean way to write XML