4   2 The human brain is an organ that has a range of functions. (a) A student produced a table linking three descriptions of brain function to a labelled diagram of the brain. Label Description of function of labelled region in brain 1 Site where more synapses are formed during the critical window for vision 2 Required for the fine motor skills to draw a straight line 3 Area that sends impulses to the sinoatrial node (SAN) in response to a lowering of blood pH Which diagram of the brain correctly matches the table? (1) 1 3 2 2 1 3 Diagram A Diagram B 3 1 2 3 2 1 Diagram C Diagram D Turn over 5   (b) There are various types of scan that can be used to study the brain. (i) Describe why a region of the brain might appear lighter in an image obtained by a functional magnetic resonance image (fMRI) scan. 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(ii) One scan combines positron emission tomography (PET) and computed tomography (CT). This scan can be used to show whether a person has cancer. Describe why a combined PET and CT scan may be better for diagnosing cancer than a PET or CT scan on its own. 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(Total for Question 2 = 7 marks)