1. Take the airquality dataset buit in R, and convert it to a tibble.

2. Take the following data.frame and tibble. Run the following operations. What do you notice about the behavior of tibbles versus dataframes?

df <- data.frame(abc = 1, xyz = "a")
df$x
df[, "xyz"]
df[, c("abc", "xyz")]

df_tib <- tibble(abc = 1, xyz = "a")

df_tib$x
df_tib[, "xyz"]
df_tib[, c("abc", "xyz")]