In each of the following letters series, some of the letters are missing which are given in that order as one of the alternatives below it. Choose the correct alternative.
aa _ _ aba _ bca _ aab _ a _

Select the combination of letters that when  sequentially placed in the gaps of the given letter series will complete the series .
gfe_ig_eii_fei_gf_ii

Select the combination ofletters that when sequentially placed in the blanks of the given series will complete the series.
 dq_pln_qt_lnd_tpl_dq_p_n

Study the given pattern carefully and select the number that can replace the question mark (?) in it.

23                32          16

3                 4              5

72              132         ?

Find the next term in the following series.
ZA5, Y4B, XC6, W3D, _____

Find the next term in the following series.
Z26, X24, V22, ____

Select the option which is related to the third number in the same way as the second number is related to the first number.
  583 : 293 : : 488 : ?

What should come in place of the question mark '?' in the following number series?
 2916, 972, ?, 108, 36, 12