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

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

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

'$= N$' is to '$T 1$' and '$B 3$' is to '$G 4$' in the same way as '$EB$' is to

What will come in place of the question mark $(?)$ in the following alphabet series?
$CD, FG, JK, ?, UV$

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?

Fill in the blank space for the given series with the correct alternative.
$90, 180, 12, 50, 100, 200, (\ldots), 3, 50, 4, 25, 2, 6, 30, 3$

Fill in the blank space for the given series with the correct alternative.
$2, 6, 3, 4, 20, 5, 6, (\ldots), 7$