df <-
  data.frame(B=c(1,0,0),
             C=c(3,4,9),
             D=c(1,1,0))

#A function to calculate stations whether there is a communication or process component or both
df <- df %>%
  mutate(combined.score = ifelse("B" %in% names(.) & "C" %in% names(.) & "D" %in% names(.), B + C + D,
                                 ifelse("B" %in% names(.) & "C" %in% names(.), B + C,
                                        B))) %>%
  mutate(combined.score.correct = B + C + D)

[1] TRUE