The correct answer is option 3: Ostrich. The ostrich is the largest flightless bird and can run at a great speed. While penguins, kiwis, and emus are also flightless birds, the ostrich is known for its incredible running abilities. Ostriches are native to Africa and are the largest birds on Earth. They have long legs and powerful muscles, which allow them to reach speeds of up to 43 miles per hour (70 kilometers per hour). Penguins, on the other hand, are excellent swimmers but are not known for their running abilities. Kiwis are flightless birds native to New Zealand and have short legs, making them slow runners. Emus, found in Australia, are known for their running speed, but they are smaller than ostriches. Therefore, the correct answer is the ostrich.