then they can watch you do it,
but you can never do it and watch each other at the same time?
(scroll down for answer)
.
BLINK
Explanation:
- “You can watch someone do me.”
- “Then they can watch you do me.”
- “But you can never do me and watch each other at the same time.”
You can observe someone blinking their eyes.
Afterward, they can see you blink in return.
If both of you blink simultaneously, your eyes are closed, so neither can watch the other.