a$.$

When the error is fixed, the resulting graph shows the data points.

b$.$

The error can be fixed by changing the location of one of the $\text{'}+\text{'}$ symbols in the code.

c$.$

The unknown expression y ~ poly$($x$,3)$ causes the error.

d$.$

The x and y in the formula of geom$\_$smooth are defined as the two arguments in aes$(,)$ on the first line of code.

e$.$

When the error is fixed, two regression lines have the same colour.