Choose the correct alternative for the missing term:
$Q1F, S2E, U6D, W21C, ?$

These questions are based on the following arrangement. Study it carefully and answer the questions.

$8 ,H ,\% ,3,7 ,T,A ,4 ,\# ,6 ,B,I ,@ ,R ,1 ,Q ,\star, L,E ,2 ,K ,\$ ,U ,5,9$

How many such symbols are in the above arrangement each of which is immediately followed by a number but not immediately preceded by another number?

Fill in the blank space for the given series with the correct alternative.
$0.5, 1.5, 4.5, 13.5, (\ldots)$ (in $.5$)

Fill in the blank space for the given series with the correct alternative.
$0, 2, 6, (\ldots), 20, 30, 42$

What should come next in the following letter series?
$nsi, org, pqe, qpc, ?$

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