Select the combination of letters that when sequentially placed in the blanks of the given series, will complete the series.
R _ _ RT _ R _ R _ TR
1
RTRRT
2
TTTRR
3
TRRTR
4
RTTTR
Select the combination of letters that when sequentially placed in the blanks of the given series, will complete the series.
R _ _ RT _ R _ R _ TR