When the children in Freezetown arrived for class yesterday, the teacher saw that 15 were wearing beanies, 8 were wearing scarves and 12 were wearing gloves. On closer inspection, he could see that all of the children wearing scarves were also wearing gloves, and that half of the children with a scarf also had a beanie. There were 4 children wearing a beanie who also had gloves but no scarf. There were 2 children with no beanie, no scarf and no gloves. How many children arrived for class yesterday? A 18 B 19 C 20 D 21