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

(a)

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

(b)

barium compound, like magnesium sulphate helps in cleaning the stomach before X-ray examination

(c)

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

(d)

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