Why is making a vaccine not a linear process???

Please help

The vaccination process consists of injecting a safe modified virus into the body to build a resistence against the harmful version. The body takes the modified version and builds the immunity against it which will protect you from catching the harmful version later on. --hope this helped!! :))

Pretty sure this would be b. the rest are trick questions. the bystanders  won't go near you if u have cpr cuffs that could hurt them. the dog will back off because the sound will scare him. and the vomits just a stupid trick. if there is that much slober and vomit on the guy hes either choking on it, or just take off his shirt.