In honor of Rio 2016, here’s a connecting wall about the Olympics! The 16 clues below can be sorted into four connected groups of 4. What are the groups and their connections?
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+--------------+--------------+--------------+--------------+
| Parry | Right of way | Middle | Extension |
+--------------+--------------+--------------+--------------+
| Fly | Bekele | Croquet | Heavy |
+--------------+--------------+--------------+--------------+
| Young | Usage | Bout | Bolt |
+--------------+--------------+--------------+--------------+
| Thrust | Walker | Bantam | Johnson |
+--------------+--------------+--------------+--------------+