Hi! This item wasn’t part of the Harder Questions video and I’m really stumped as to why the answer is A, and not D – my thinking is you can move X around such that angle RXS is greater than, equal or less than RTS.
Can someone help shed some light on this, please? 
TIA!
P.S. I’m on my 5th week following the 2-month plan and I find all the resources so helpful. Thank you, GregMAT team, and all the best to everyone preparing for their best GRE performance!