Series Completion - Verbal and Reasoning

Directions to SolveIn each of the following letter series, some of the letters are missing which are given in that order as one of the alternatives below it. Choose the correct alternative.
Q1:

_ stt _ tt _ tts _

A tsts

B ttst

C sstt

D tsst

ANS:D - tsst

Explanation: The series is tst/tst/tst/tst. Thus, the pattern 'tst' is repeated.