Teacher:In this task, you will be given sentences in which your task is to recognize the name of the organ of the body. An organ is a collection of tissues that structurally form a functional unit specialized to perform a particular function. Although there might be several correct answers, you need to write one of them.
Teacher: Now, understand the problem? Solve this instance:  In this report we assess the systolic maximal flow velocity in carotid and intracranial arteries in 191 subjects with no history of cerebral vascular disease in 3 age groups : 20 - 40 years ( 1 group ) , 41 - 60 years ( 2 group ) , and above 60 years ( 3 group ) .
Student:
cerebral