Choose the correct alternative to fill in the blanks in the series: $ab...bcbca...c...bab$

Which number will come next in the following series?
$2, 1, 2, 1, 3, 2, 1, 3, 4, 2, 1, 3, 4, 5, 2, 1, 3, 4, 5, 6, 2, 1, 3, 4, 5, ?$

To answer these questions, study the following arrangement of digits, letters and symbols carefully.

$6, N,P ,=,@, 7,1 ,\& , R, T, 3, L, ,B, \star, E ,4,\# , 8, G,H ,\$, 5, K,M ,?, 2, D,C$

If all the symbols in the arrangement are deleted, which of the following will be the $4^{th}$ to the left of the $12^{th}$ element from the left end?

Study of the following arrangement carefully and answer the questions given below.

$Q,E ,* ,P,M ,8 ,R,A ,@ ,C ,9 ,U,H,W, \# ,J,Z, ,S, \beta, Y,N ,5 ,\$ ,G,I,T$

Which of the following is exactly in the middle between the twelfth from the right and the seventh from the left end?

Which term comes next in the sequence: $nd, iy, dt, yo, tj, ?$

Fill in the blank space for the given series with the correct alternative.
$1, 8, 27, 64, 125, 216, (\ldots)$