1. 

What should come in the place of question mark (?) in the following alpha numeric series?

A1, C3, F6, J10, O15, ?

A. U21
B. V21
C. T20
D. U20

Answer: Option A

Explanation:

Pattern of the series as shown below

letter-and-symbol-series-logical-reasoning-practice-level---letter-and symbol-series-problems

Hence, the missing term is U21.