Please answer the following question: Read the following article and select the best answer. Article: Many people rely on a cup of coffee or two to wake them up in the morning or refresh them during the working day, but now a chemist has come up with a speedy alternative to drinking coffee. U.S. biochemist Ben Yu has created 'Sprayable Energy', which claims to be the world's first caffeine - based topical energy spray. He said tired workers can spray a 'shot' of caffeine onto their skin without experiencing a strong noise, taking in unnecessary calories or being stuck with a nasty aftertaste like they might get from drinking energy drinks or coffee. The tasteless caffeine spray is absorbed through the skin and spread through the body over a number of hours to deliver a caffeine hit that lasts longer than drinking a cup of coffee. The only active ingredient in the spray is caffeine, which is very similar to nicotine in structure. Each spray 'Sprayable Energy' contains around a quarter of the amount of caffeine found in a cup of coffee, but apparently has the same effect as a full cup. The website said: "The reason for this is our product isn't entirely metabolized by the liver before entering your system and becoming available to your body." Sprayable Energy's website recommends that users apply the spray in places where they normally spritz perfume, such as wrists, the neck or behind the ears, but warns users not to exceed 20 times a day. It claims that after spraying the product on the skin, users will feel awake and focus without being over-excited, which is common with coffee and energy drinks. Question: Which of the body may not be suitable to apply "Sprayable Energy"? - The neck. - Behind the ears. - Wrists. - Mouth.
Answer:
Mouth.