Find out the wrong term from the given series.
$1, 2, 6, 15, 31, 56, 91$

Choose the correct alternative to fill in the blanks in the series: $...c...bd.....cbcda.....a...db...a$

Fill in the blank space for the given series with the correct alternative.
$2, 6, 12, 20, 30, 42, 56, (\dots)$

Fill in the blank space for the given series with the correct alternative.
$2, 5, 9, 19, 37, (\ldots)$

Find out the missing term for the given series from the given alternatives.
$P 3 C, R 5 F, T 8 I, V 12 L, ?$

In the number $76534218$,each digit is replaced by the next digit (i.e.,$1$ is replaced by $2$,$2$ is replaced by $3$,and so on). After this,the digits are arranged in ascending order from left to right. Which digit will be fifth from the left end?