The claim that is best supported by the text evidence in this passage is:
Shere Khan places all of the jungle animals in danger by breaking the law of the jungle.
The passage explains that the law forbids the killing of humans because it leads to consequences that affect all animals, specifically the arrival of humans with guns and other destructive measures. This implies that breaking the law by killing a human (like Mowgli) threatens the safety of all animals in the jungle.