Answer:
b. Garnett's negligent driving is the proximate cause of John's injury.
Step-by-step explanation:
It is clear that Garnett's driving is negligent in this case. Since John was was walking down the street near the site of the collision hence even if the truck did not have explosive material Garnett's driving could have injured John. This means that the proximate cause of John's injury was Garnett's negligent driving. But the same cannot be said about Ida who was a block away from the collision site and only got injured because of the explosive material in the truck. Since the truck was unmarked hence Garnett cannot be held responsible for Ida's injuries.