Which of the following is true about using comments in a program?

Select one or more:

a$.$ Comments can be used to describe the purpose of a chunk of code.

b$.$ A program will not execute correctly without comments.

c$.$ Comments can be used to describe the purpose of the entire program.

d$.$ In SAS Studio, commented code turns a different color to indicate it is a comment.

e$.$ Comments improve the computational speed of a program.

f$.$ A $*$ is one way to indicate the beginning of a comment statement in SAS.