In the following question, select the number which can be placed at the sign of question mark (?) from the given alternatives. 

Select the letter-pair that can replace the question mark (?) in. the following series
BA, DC, FE, HG, ? , LK

Which number replaces the question mark?

Which numbers replace the question mark

In the following question find out the missing number?

In the following question, select the number which can be placed at the sign of question mark (?) from the given alternatives.

A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.
I, L, O, R, ?

In the given figure select the number that can replace the question mark (?).