Multiple choice general knowledge If the cheetah is the fastest thing on four legs, what is the fastest on two legs? Kangaroos Penguins Men Ostrich Reveal answer Fill a bubble to check yourself D Correct answer Explanation Ostriches are the fastest birds on land and the fastest bipeds, reaching speeds up to 70 km/h. Kangaroos hop powerfully but cannot match ostrich speed, penguins are adapted for swimming, and humans are much slower.