Space Exploration is the investigation of the universe beyond Earth’s atmosphere by (1) _______________ of manned or unmanned spacecraft.

Choose the word or phrase among A, B, Cor D that best fits the blank space in the following passage.

Space Exploration is the investigation of the universe beyond Earth’s atmosphere by (1) _______________ of manned or unmanned spacecraft. Despite the technological advancements achieved in the past, space exploration was only (2) ________________  until the 20^th century. The first successful orbital launch was made by the Soviet Union 1957 which was called “Sputnik”. When the topic “SPACE OPERATION” is put (3) _______________ the table, a question has often been asked:

“Why should we spend money on NASA while there are so (4) ______________ problems here on Earth?”. However, this might be partially wrong exploring the unknown may help us progress. The advantages of space exploration include the materials (5) ______________ can be obtained from outer space. For instance, asteroids have iron and nickel which could be utilized to satisfy the (6) ______________ for metal. Therefore, numerous commercial companies have invested in developing technology for asteroid mining. Several comets and asteroid (7) ______________ solid water in them. This water can be used for astronauts and scientists in space stations. The water can also be broken down to hydrogen which can be used as (8) _____________ for the rockets. Scientists also believed that dinosaurs disappeared because they couldn’t go to (9) _____________ planet. Sooner or later a killer comet will again cross Earth’s path , threatening all life. Fortunately, (10) _____________ we have knowledge about comets and space science, we will be able to survive. 

(1) .......................

• A. ways
• B. means 
• C. the time
• D. which