[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