Answer:
The crab has just molted and the new exoskeleton has not yet hardened.
Crabs have an exoskeleton or shell which protects and supports them. From time to time crabs molt i.e. they discard the old exoskeleton and begin forming a new one. This process is a part of their normal growth. Soft-shell crabs had recently undergone molting and the new shell had just started to form. Hence, it has not hardened completely and is comparatively soft. Soft-shell crabs are in popular demand because it is easier to remove the soft shell and access the meat as compared to the normal crab.
Step-by-step explanation: