How does the vampire used to make the filmmaker believe Nick die?  Answer the above question based on the context below:  Aspiring filmmaker Sean is working as a freelance driver to make ends meet. He's assigned to deliver an expensive Mercedes-Benz from Los Angeles all the way to its owner in Miami, which will also allow him to attend the wedding of his sister. He's given strict instructions not to damage the vehicle or pick up any hitchhikers. Sean is driving cross country when he picks up Nick, a hitchhiker who happens to be a vampire hunter hunting a group of vampires led by one of the Forsaken--a group of knights who made a pact with the fallen angel Abaddon to live forever. Two of the Forsaken are located in the United States (including the one Nick is tracking, Kit). Nick was bitten and infected by a vampire but, thanks to an antiviral drug cocktail, the vampire virus is kept at bay. Each of the Forsaken carry a unique strain of vampirism; killing a Forsaken kills his entire bloodline and reverses the condition of anyone infected. Nick believes that if he kills Kit, he will be cured before he turns (as the drug cocktail eventually will lose effect). At first Sean is less than willing to indulge his new acquaintance; however, he is convinced after the two come across a disoriented young woman, Megan, at a diner, who was bitten by the vampires and left for dead. Nick also proves he is telling the truth by killing a vampire, Teddy, with exposure to sunlight. Sean and Nick take Megan to their motel room, but she goes into a rage and bites Sean; they realize they must kill the Forsaken responsible to prevent Sean from turning. Forsaken can only be slain on hallowed ground, so the three head for a Spanish mission 60 miles away. They stop at a gas station where an old woman, Ina, lets them in. She shows them a newspaper connecting Megan to a bloodbath in Arizona; when Megan wakes up and is coherent enough to talk, she explains she was a victim of the vampires' bloodbath. Kit catches up to them and lays siege to the gas station.
The answer to this question is:
exposure to sunlight