In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".

Ex Input:
[header] How to stay up late without electronics [title] Drink caffeine. [step] Caffeine blocks neurotransmitters in your brain that make you sleepy. When you start to feel drowsy, reach for a cup of coffee or a soda. <sep> (A) Remember that caffeine loses its effectiveness with overuse. Try to save it for when you really need it. (B) Your body will start shutting down caffeine when you're outside and keep you awake by doing what it is meant to do. It can help you stay awake long enough to go to bed. (C) Though caffeine will not give you energy right before sleep, it will trigger the natural sleep signal that draws us into the world right before it hits. An caffeine-rich beverage will wake you up more, making your sleep better. (D) Coffee is the source of human sleepiness so drinking coffee or another caffeinated beverage before bedtime is important. Even an extra pill is a key lubricant.

Ex Output:
A

Ex Input:
A small group of children are seen standing before a mat with an instructor helping. the girls <sep> (A) then begin throwing a rope to the back and covering the boys head with the rope. (B) then pole vault on the mat and swing during a routine. (C) do various gymnastics moves across the mats while an instructor assist them and another points to the side. (D) take turns running to the mat and pushing it down.

Ex Output:
C

Ex Input:
[header] How to bathe a pregnant guinea pig [title] Select a shampoo. [step] There are all types of shampoos for pets. For your guinea pig, make sure the shampoo is made specifically for small animals (it should say so on the bottle). <sep> (A) Otc shampoos and chemical shampoos are good choices. Avoid shampoo labeled specifically for guinea pigs and those formulated for females. (B) This way, both animals can use the shampoo and their fur will be clean. While many shampoos claim to free your guinea pig from " reye's syndrome ", this actually isn't true. (C) [substeps] Make sure that it is specially formulated for pregnancy-therefore not designed for your guinea pig. You can get shampoo from the veterinarian. (D) A small animal-specific shampoo will keep your guinea pig's skin from drying out or becoming irritated. Since your guinea pig is pregnant, the shampoo should also be non-medicated to prevent ingredients absorbing through her skin that could harm her unborn babies.

Ex Output:
D