Complete the following series –
_ _ aba _ _ ba _ ab

In the word INSTRUCT, how many alphabets are there between which there are as many letters as there are between them in the English alphabet? 

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

BDE, CFG, EJK,  ?

A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.
 LOG, FLH, ZII, TFJ, NCK,?

In the following question , a series is given with one terms missing . Choose the correct alternative from the given ones that will complete the series :

ABC , DEF , HIJ , ? 

Select the term that will come next in the following series?
CAY, FDB, IGE, ?

How many such pairs of letters are there in the word MEDIOCRE each of which has as many letters between them in the English alphabet series? 

What comes in place of question mark (?) in the series given below?
W-144, ?, S-100, Q-81, O-64