Barium in a suitable form is administered to patients before an X-ray examination of the stomach, because

A barium salts are white in colour and this helps the stomach to appear clearly in contrast with other regions in the picture

B barium is a good absorber of X-rays and this helps the stomach to appear clearly in contrast with the other regions in the picture

C barium is a good absorber of y-rays and this helps the stomach to appear clearly in contrast with the other regions in the picture

D barium allows X-rays to pass through the stomach on account of its transparency to X-rays