A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.

Narendra Modi, Manmohan Singh, Atal Bihari Vajpayee, ?

A series is given with one term missing. Choose the correct option from the given ones that will complete the series.

50 : 70 ::..?.... 90

2, 10, 30, 68, ?

Select the number from among the given options that can replace the question mark (?) in the following series

237, 196, 155, 114, ?

A series is given with one term missing. Choose the correct option from the given ones that will complete the series.

2 : 7 : 4 : 9 : ?

A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.

Millimetre, Micrometre, Nanometre, ?

Select the letter-pair that can replace the question mark (?) in the following series.

AR, CU, EX, GA, ?

Which of the following numbers will replace the question mark (?) in the given series?
 17, 20, 60, 64, 256, 261, 1305, ?