Which system consists of the body’s outer covering?

It begins with cells, tissues, organs, organ system to organism. There are 11 organ systems that work collectively for an organism to function. Each organ is responsible for a different function and has its own structure. The organism system that consist of the body's outer covering is the integumentary system. It consist of skin, hair, nails, and endocrine glands; they are the protectors of the body. The environment such as UV rays are harmful and the skin, hair, nails, etc protect the body as needed. 

Number one is sinkholes may form from water erosion

Nimbostratus is the correct answer.
explanation: nimbostratus clouds are the type of clouds that are mostly likely present on gray, rainy day. these clouds produce continuous rain, snow and there is no thundering or lightening either.