Our Earth

0°

0° is the correct answer. The Prime Meridian is the longitude line designated as 0° that passes through Greenwich, England. It serves as the starting point for measuring all other longitudes. 180° is the anti-meridian (opposite to Prime Meridian), while 90° East and 90° West are just regular longitude lines. The Prime Meridian also serves as the reference point for calculating time zones around the world.

365¼ days

365¼ days is the correct answer. Earth takes exactly 365¼ days to complete one full revolution around the Sun, which we call a year. This is why we have a leap year every four years to account for the extra quarter day. 24 hours is the time for Earth's rotation on its axis (one day), not revolution around the Sun. 30 days is approximately one month, and 12 months exactly would be 360 days, which is not accurate for Earth's orbital period.

Iron and Nickel

Iron and Nickel is the correct answer. Earth's core, both outer and inner, is composed primarily of dense metallic materials like iron and nickel. These heavy elements sank to the center during Earth's formation when the planet was in a molten state. Silicates make up the mantle, rocks form the crust, and water exists on the surface and in the atmosphere, but none of these constitute the core's main composition.

Northern Hemisphere

Northern Hemisphere is the correct answer. The Northern Hemisphere contains most of the world's landmass, including large continents like North America, Europe, Asia, and most of Africa. The Southern Hemisphere has more ocean area and fewer large landmasses. While the Eastern and Western hemispheres also contain significant landmasses, the Northern Hemisphere has the greatest concentration of continental land area.