Practicality means that the subject matter of an invention or utility model application must be able to be manufactured or used in industry and produce positive effects. Item A is obviously practical.
Item B is a surgical method for non-therapeutic purposes. Because it is carried out on living people or animals and cannot be used in industry, it is not practical.
Item C belongs to the method of measuring physiological parameters of human body or animal body under extreme conditions, which needs to put the measured object in extreme environment and will pose a threat to human body or animal life. Different people or animals can tolerate different extreme conditions, and experienced testers need to determine their tolerance limit conditions according to the conditions of the tested objects, so this method can not be used in industry and is not practical.
Item D belongs to an application for a patent for invention or utility model that violates the laws of nature and cannot be implemented. So it is not practical.