Fill in the blank space for the given series with the correct alternative.
$20, 19, 17, (\ldots), 10, 5$

How many such pairs of digits are there in the number $7326985$ each of which has as many digits between them in the given number as when the digits of the number are rearranged in ascending order within the number?

Choose the correct alternative to fill in the blanks in the series: $abca....bcaab....ca....bbc...a$

Study carefully the following arrangement of letters, digits and symbols to answer these

questions.

$M, 7 ,\&, 8, L ,P ,@ ,Q ,N ,\beta ,T ,Y ,3 ,2 ,= ,E ,\$ ,4 ,9 ,\#, G ,H ,5$

$'78'$ is to $'P?6'$ and $'?N'$ is to $'T32'$ in the same way as $2 E'$ is to $\ldots \ldots \ldots . . .$ in the arrangement.

Fill in the blank space for the given series with the correct alternative.
$3, 4, 7, 7, 13, 13, 21, 22, 31, 44, (\ldots)$

Find the missing letters for the given series from the given alternatives:
$aab....ab....cabcca....bcab....c$