Which body tissue has CT numbers that are closest to that of blood?

The choice indicating that "most body tissues" have CT numbers closest to those of blood is correct because blood, with its liquid and soft tissue characteristics, generally exhibits CT numbers that fall within a range similar to various soft tissues in the body.

CT numbers, measured in Hounsfield Units (HU), reflect the density of the material being scanned. Blood generally has a CT number around 30 to 40 HU. Common soft tissues, such as muscles and organs, typically exhibit similar ranges, making them comparable to blood in terms of CT imaging.

While muscle can have CT numbers somewhat close to blood, they usually range higher than that of blood, typically between 40 to 60 HU when considering muscle at rest. Fat, on the other hand, has a much lower CT number, usually around -100 to -50 HU, and bone has a significantly higher CT number due to its density, often exceeding +300 HU. Therefore, "most body tissues" as a category encompass a wide variety of tissues that can have CT numbers close to blood, validating the selection of this answer as the best to represent the average behavior across various tissues in CT imaging.