What will come in place of question mark(?) in the following number series?

BCF, CDG , DEH, ?

Complete the series.
TEA, UFB, ?, WHD

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

In each of the following question , find the missing letters from the given response.
HIIJ, IJJK, JKKL,  KLLM,  LMMN, ?

6, 42, ?,  1260, 5040, 15120, 30240

Find the next term in the given series.
 1200, 600, 300,  ?

Select the option that will fill in the blank and complete the given series.
7, 16, 40, 84______252

What will be the next number in the given series?
  3, 28, 4, 65, 5,126,6,.........?