Answer:
B) No, because everyone knows that glass doors can be run into, and therefore the manufacturer does not have to provide such a warning.
Step-by-step explanation:
Gunter needs to sue himself for not having any common sense. I really doubt that anyone that installs a glass doesn't know that they are transparent and that people must be careful when they approach them because accidents may happen. For instance, you can hurt yourself and/or you can break the glass door.
This is similar to buying a car and after crashing it, the owner sues the car manufacturer for not preventing him from driving. Almost every product that you buy or everything that you find at home can potentially harm you. E.g. you can poke an eye with a fork, knife, pencil, even a spoon, and probably many more items, but is anyone going to do so just because the item is at their house?