Select the combination of letters that when sequentially placed in the blanks of the given series will complete the series.

_uvwuv_wvtuw_uvwuv_wv_uw

t t t t t

By observing all the options , We find that only option 1 will form the series with repeated pattern .

Pattern followed is :

"tuvw" is written in alphabetical order and w, the 4th letter remains constant. Only tuv changes its place alternatively like tuv, uvt and vtu.

 _uvwuv_wvtuw_uvwuv_wv_uw