Nacre also known as mother of pearl, is an organic-inorganic composite material produced by some mollusks as an inner shell layer; it is also what makes up the outer coating of pearls. It is strong, resilient, and iridescent.

New Moore Island was known as New Moore Island in India and South Talpatti Island in Bangladesh. It was an unhabitated island which emerged in the Bay of Bengal in the aftermath of the Bhola cyclone in 1970. It had been created by the delta currents. It was located south of the Hariabhanga river. Now it has disappeared due to raising sea levels. 
 

Open sky refers to an agreement between two countries to allow any number of airlines to fly from either of them without any restriction on number of flights, number of destinations, number of seats, price and so on. However, this is a general definition. In actual practice, there are always some restrictions.

Sedimentary rocks are made from layers, or strata, of mineral particles found in other rocks that have been weathered and from newly formed organic matter.  Sedimentary rocks are important because they preserve a record of ancient landscapes, climates, and mountain ranges, as well as the history of the erosion of Earth. In addition, fossils are found in abundance in sedimentary rocks younger than 600 million years and provide evidence of the evolution of life through time. Earth’s geologic time scale was worked out using this record of sedimentary rocks and fossils.