this question can be solved with 2 ways.
1) NODE MERGING
if we apply node merging..then height will decrease...
and if we apply re-distribution height remains same..
so statement 1 is true if we apply re-distribution
statement 2 is true...as we know 20 will remain present
statement 3 cannot be true in either case
whether it is node merging or re-distribution ROOT NODE will change surely....in both case
so option 1 matches only
and option ALL FALSE is not true becoz statement 2 is always true 20 will remain inside the tree