Which of the following is correct? a. A group function can be nested inside a group function. b. A group function can be nested inside a single-row function. c. A single-row function can be nested...

Which of the following is correct?

a. A group function can be nested inside a group function.

b. A group function can be nested inside a single-row function.

c. A single-row function can be nested inside a group function.

d. a and b

e. a, b, and c