What substance is used in medicine to produce various images of organs and tissues?

The substance like iodine 131 is used as in medicine which can help produce various images of organs and tissues. This substance is called as a tracer. Iodine 131 is a radioactive isotope which is also used to monitor thyroid gland functioning, to locate tumours in the liver or brain, and also treat thyroid cancer.

the correct answer is 2 and 4

evidence and logical support is essential for a scientist to do in order to maintain credibility. this is because no one can believe without any logic and without any evidence.hence a scientist can maintain credibility by proving himself and by answering logically so experiments prove very beneficial. logical hypothesis give conclusion which is acceptable. therefore, there are two main factors to maintain credibility by a scientist is evidence and logical support.