umaa wrote:[spoiler]OA is E. I was stuck between D and E and I finally chose D because, in E BY reducing needs to be parallel with BY letting, not LETTING. Any idea why E is correct without BY parallelism? its a OG question.[/spoiler]
Yes, IMHO should be E.
To answer your question,
"by reducing...and letting..." instead of "by reducing......and by letting....." doesn't change the meaning atleast, though may not be very parallel.
Where as in D the use of words "when reducing" doesn't make any sense.
