What is the shortcut key to "Undo" the last action in a

Based on the relationship between first two words, find out the missing word.

Amphibian: Frog ::   Terrestrial: ?

Tree : Shrub :: Mountain : ?

Hawa Mahal : Jaipur :: Victorial Mahal : (?)

Select the option that is related to third letter-cluster in the same way as the second letter-cluster is related to the first letter-cluster.

520 : 648 :: 128 : ?

GIKM : JNRV ∷ IKMO : ?

Select the related word/letters/number from the given alternatives.

CF : JM :: QT : ?

Select the option in which the numbers are related in the same way as the numbers of the following set:

(5, 500, 10)