Geography · Oceanography

Consider the following statements regarding oceanic relief and underwater mountain features: 1. Many of the world's largest mountain chains exist completely submerged beneath the oceans. 2. Some underwater mountain chains breach the surface and are revealed as island arcs. 3. The mid-oceanic ridges form the longest continuous mountain chains on Earth. 4. The Mid-Atlantic Ridge floor depth is uniform, rising exactly thirty-three metres above the ocean floor everywhere. Which of the statements given above are correct?