(A) The culture and tradition of the local people will be influenced by the tourists.
There is no information about the culture and tradition of local people.
So, this option is discarded.
(B) The region will become crowded and polluted due to tourism.
This is already written in the paragraph itself.
So, this option is discarded.
(C) The coral reefs are on the decline and could soon vanish.
There is no information about declination of the coral reefs.
So, this option is discarded.
(D) Helicopter connectivity would lead to an increase in tourists coming to the region.
This option can be logically inferred from the above paragraph
So, this is the answer D)