Number of letters skipped in between adjacent letters in the series are increased by one. Which of the following alternatives observes this rule?

The number of letters skipped between adjacent letters in the series follows the order of $2, 5, 7, 10$. Which of the following series observes the rule given above?

Arrange the given words in alphabetical order and choose the one that comes in the middle.

If the first and second letters in the word $DEPRESSION$ were interchanged,also the third and the fourth letters,the fifth and the sixth letters and so on,which of the following would be the seventh letter from the right?

How many meaningful words can be made from the letters $ACER$ using each letter only once?

$A$ 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 the combination of numbers so that the letters arranged accordingly form a meaningful word.
$R, T, E, O, D, P$
$1, 2, 3, 4, 5, 6$