In the article "Science of Star Wars: How Scientists Use the Force", Phillips says robotics scientists can be classified into two types: the R$2$D$2$ type and the C$3$P$0$ type. What do those who are R$2$D$2$ types care most about?

a$.$ The programming language used to program the robot

b$.$ The robot's form

c$.$ The robot's mobility $($i$.$e$.,$ how it moves around$)$

d$.$ The way the robot communicates with people