Right choice is (a) glucose
To explain: For any growing or recovering part of the body, the most important content is carbohydrate which is provided by glucose. Thus, to test for a suspected malignant tumour, a glucose based radioligand is used. This radioligand is absorbed by a tumour and it collects and becomes part of the normal functioning of the body. The more the collection of the radioligand at one place, greater is the size or the activity of a tumour.