Find the missing letters for the given series from the given alternatives.
$ba.....ba.....bac......acb......cbac$

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?

Find out the wrong term from the given series.
$46080, 3840, 384, 48, 24, 2, 1$

Study the following arrangement carefully and answer the question given below:
$R, 4, E, J, 5, T, 1, A, M, Q, 3, 8, N, I, K, 7, W, F, 6, D, 9, U, 2, Y, V$
Which of the following is exactly in the middle between $A$ and $D$ in the above arrangement?

Choose the alternative that will complete the series:
$aku, fpz, kue, (\ldots), ueo, zjt$

Fill in the blank space for the given series with the correct alternative.
$2, 15, 41, 80, (\ldots)$