In the following question find out the missing number?

Choose the correct option from the following options.
AZYB : CXWD ∷ BYWD :?

Kanna is taller than Malik. Dev is shorter than Krish where as Krish is taller than Malik. Veena is shorter than Krish but taller than Malik and Dev is taller than Veena. Who is the Shortest ? 

aa_baa_aaa_ba_ba

Directions : In each of the following letter series, some of the letters are missing which are given in that order as one of the alternatives below it.

ab ---b -bbaa- 

A tourist travelled 10 km in the west and went 4 km after turning to the left. Then he travelled 4 km. in the East and went 5 km. after turning to the right. Then he travelled 6 km. after turning to his left. Find his direction regarding the starting point.

Cosider the given argument and decide which of the given assumptions is (are) implicit.
Argument:
Due to water crisis in the city, the authority had asked all the citizens to reduce their water consumption by 25%.
Assumptions:
1. Many citizens may reduce their water consumption.
2.Many activists may protest to this advisory by the authority.

Dinesh is older than Ramesh. Boman is younger than Dinesh. Who is the youngest of all.