Kai was a little worried about History of Magic, he'd heard the professor was pretty strict and he certainly didn't want to get on his bad side. Luckily for him, he had a good answer to the first question at hand.

"It was stolen from Crewe and adopted as the only allowed form of transportation to Hogwarts - if you didn't use the Hogwarts Express then you didn't study for the year. I can't remember who came up with the idea, but it was seen as the solution to the mass muggle sightings of witches and wizards carrying hefty trunks on broomsticks each September. Originally portkeys were used as a solution, but many students missed their portkey slots as they couldn't find the objects they were meant to be using to transport - probably because they were small muggle objects that were intentionally bland to pass unnoticed."

Hopefully that was a good enough answer to please his professor, being on his good side would make lessons much more enjoyable this year.