Steatite is a very soft stone. It is also known as soapstone and is a type of metamorphic rock. It is composed mostly of talc, which gives it its characteristic softness. Steatite is commonly used for carving and sculpting due to its ease of shaping.

- **Steatite**:
Steatite is a very soft stone and is considered one of the softest minerals on Earth. It has a hardness of only 1 on the Mohs scale, which makes it easily scratchable with a fingernail. This softness is due to its high talc content, which gives it a greasy or soapy feel.

- **Jasper**:
Jasper, on the other hand, is not a soft stone. It is an opaque variety of chalcedony, which is a type of quartz. Jasper is known for its hardness and durability. It has a hardness of around 6.5 to 7 on the Mohs scale, making it much harder than steatite.

- **Carnelian**:
Carnelian is another type of chalcedony and is also not a soft stone. It is a translucent variety of quartz that ranges in color from pale orange to deep red. Carnelian has a hardness of around 6.5 to 7 on the Mohs scale, similar to jasper.

Therefore, the correct answer is option 'A' - Steatite. Steatite is a very soft stone due to its high talc content, while jasper and carnelian are harder stones.