What does the SELECT ASSIGN clause do in this snippet of code:

select one:

a$.$

Selecting the internal file name, PRINT$-$LINE, and assigning it to the external file$/$data set, PRTLINE.

b$.$

Selecting the external file name, PRINT$-$LINE, and assigning it to the internal file$/$data set, PRTLINE.

c$.$

Selecting the internal file name, PRINT$-$LINE, and assigning it to the internal file$/$data set, PRTLINE.

d$.$

Selecting the external file name, PRINT$-$LINE, and assigning it to the external file$/$data set, PRTLINE.