Questions

The given statement, The heat from the sun reaches earth through Convection is FALSE.

Heat from the sun actually reaches the earth through Radiation. The process occurs through electromagnetic radiation, specifically, in which molecules are warmed when the heat reaches them, and these molecules then warm other molecules touching them, which continues until we feel the sun's heat.

Silver nitrate is the basic substance from which silver bromide is obtained. The photographic films are impregnated with the light sensitive AgBr.

The logic in the given puzzle is 

Addition of numeric values of corresponding letters in the first three figures gives respective corresponding letter in fourth figure. 

i.e, A = 1 , W = 23 , B = 2 => 2 + 1 + 23 =26 = 'Z'

Similarly, L = 12, K = 11 , A = 1 => 1 + 11 + 12 = 24 = 'X'

Here the missing letter is 'X'.