Option 1 is true. The International Date Line is located at the 180° longitude line. This imaginary line is halfway around the world from the Prime Meridian (0° longitude) and serves as the dividing line between two consecutive calendar days. When you cross this line from west to east, you move the clock forward 24 hours or one day, and when you cross it from east to west, you move the clock back 24 hours.

Option 2 is incorrect as it is not a straight line. It looks straight on most maps but actually bends and curves to accommodate political boundaries and avoid dividing certain territories.

Option 3 is incorrect as the International Date Line is not a big circle, it is a line that extends from the North Pole to the South Pole, dividing the Pacific Ocean into two hemispheres.

Option 4 is incorrect as the International Date Line is not curved beyond the Earth. It is a purely imaginary line established for practical and convenience purposes.