In the following question, a group of letters is given which are numbered 1, 2, 3, 4, 5 and 6. Below are given four alternatives containing combinations of these numbers. Select that combination of numbers so that letters arranged accordingly, form a meaningful word.
R E S T L U 1 2 3 4 5 6
In following number series, two terms have been put within brackets. Choose the appropriate option - Find out the missing number in the following sequence :1, 3, 3, 6, 7, 9, ?, 12, 21.