A characteristic of all chordates at some point during their life cycle among four options is Post anal tail.

Explanation:
Chordates are a group of animals that includes fish, amphibians, reptiles, birds, and mammals, including humans. They are named after the presence of a notochord, a flexible, rod-like structure that runs along the back of the animal.

Following are some major common characteristics of chordates:
1. Notochord: A flexible, rod-like structure that runs along the back of the animal.
2. Dorsal hollow nerve cord: A nerve cord that runs along the back of the animal, and eventually develops into the brain and spinal cord.
3. Pharyngeal slits or pouches: Paired openings in the throat that function in filter-feeding or gas exchange.
4. Post-anal tail: A tail that extends beyond the anus.

In addition to these four key featres, chordates also have a number of other shared characteristics, such as a closed circulatory system, a well-developed brain, and a muscular system that includes a segmented body structure.