1. First touch the crab's eyes lightly with chopsticks, and pay attention to see if its eyes move. If there is no movement, it may be dead/pretend to be dead.

2. Put the crab into the prepared small basin of water and pay attention to whether there are bubbles coming out of the crab's mouth. If there are bubbles coming out, it means the crab is relatively fresh.

3. Cut the rope of the crab, put the crab in the basin, use two chopsticks to pull the crab's legs apart, and check whether the crab legs are alive and whether they bend back naturally. If it's slow, or doesn't move, the crab is dead/stale.