Which garment is described as having a bag-like shape with sleeves and cuffs that can be folded over?

The correct choice is identified as a sleeper. A sleeper is a one-piece garment, typically designed for infants or young children, and is characterized by its bag-like shape. This design is particularly functional as it allows for ease of movement while keeping the child warm and comfortable.

The sleeves and cuffs that can be folded over add to the versatility and practicality of the sleeper. This feature is useful as it can serve to keep the child's hands warm or to prevent them from scratching themselves during sleep. Additionally, the bag-like structure provides a safe sleeping environment by allowing for free movement without restriction.

In comparison, a coverall generally refers to a type of outer garment that covers the entire body and is not specifically designed for sleeping. A sleeping gown might suggest a loose-fitting nightgown for adults or children but does not embody the same shape or functionality as the sleeper. Meanwhile, a sleep sack is similar to a sleeper but typically does not feature sleeves; instead, it is more of a wearable blanket, thus differing in structure and intended use.