Questions

It has been said that the creation of NASA was due to the space exploration race between the US and the Soviet Union. One of the drives to the creation of NASA is the launching of Sputnik on October 4, 1957.

Since then, further explorations have been made by the agency.

The logic in this puzzle is summing the result of [subtraction of upper two digits] & [addition of lower two digits] 

Hence, the result is  

(5 - 3) + (2 + 8) = 2 + 10 = 12.

Answer:  U

Explanation:  Start with the D on the outer left of the diagram, and move clockwise around the outer segments, then start on the N anti-clockwise around the inner segments. Letters advance through the alphabet in steps of 3, then 4, 5, and 6, repeating this sequence.

Sevagram

In the bond formation of barium with oxygen, the valency electrons from the barium transferred to the oxygen and forms an ionic bond.

A person who insists on something unyieldingly is called a Stickler.