Answer:

' Do repeatedly:
'   Ask the user for a note.
'   Play it for about a second.
'   (The user enters a note less than 37 to stop.)
'
PRINT "Enter the frequency (37-32000):"
INPUT FREQ
DO WHILE FREQ >= 37
  . . . do something or other  . . . 
  PRINT "Enter the frequency (37-32000):"
  INPUT FREQ
LOOP
PRINT "Done!"
END

Lower Limit

There is only the "... do something or other ..." blank in the loop body that needs to be filled in. Use the SOUND statement:

SOUND frequency,duration

QUESTION 21:

Fill in the loop-body blank.