Read the following passage and choose the letter A, B, C, or D to indicate the correct option that best fits each of the numbered blanks

Ha Long Bay is a UNESCO World Heritage Site and popular travel ___(1)___ in Quang Ninh Province, Vietnam. The bay features thousands of limestone karsts and isles in various shapes and sizes. Ha Long Bay is a center of a larger zone which ___(2)___ Bai Tu Long Bay to the northeast, and Cat Ba Island to the southwest.
Ha Long Bay has an area of around 1,553km2, including 1,960 - 2,000 islets, most of which are limestone. The core of the bay has an area of 334km2 with a high density of 775 islets. The limestone in this bay has gone through 500 million years of ___(3)___ in different conditions and environments. The evolution of the karst in this bay has taken 20 million years ___(4)___ the impact of the tropical wet climate. The geo-diversity of the environment in the area has created biodiversity, including a tropical evergreen biosystem, oceanic and sea shore biosystem. Ha Long Bay is ___(5)___ to 14 endemic floral species and 60 endemic faunal species.