What should come next in the following letter series?
$H, G, F, E, D, C, B, A, H, G, F, E, D, C, B, H, G, F, E, D, C, H$

The positions of the first and the fifth digits in the number $53216894$ are interchanged. Similarly,the positions of the second and the sixth digits are interchanged,and so on. Which of the following will be the second from the right end after the rearrangement?

Find out the wrong term from the given series.
$56, 72, 90, 110, 132, 150$

Study the following arrangement carefully and answer the question given below.
$Q, E, *, P, M, 8, R, A, @, C, 9, U, H, W, \#, J, Z, S, \beta, Y, N, 5, \,G,I,T$
How many such vowels are there in the above arrangement,each of which is immediately followed by a symbol?

The following questions are based on the five three-digit numbers given below:
$972, 526, 487, 359, 251$
If the digits in each of the above numbers are written in reverse order,which will be the second highest number?

Choose the correct alternative to fill in the blanks for the series: $a . c a c b c . . . b a c a . . . b$