For each of the three situations below, choose a radio-nuclide from those studied and explain why its attributes make it suitable to the imaging method in question: i) Gamma camera scans to establish kidney function ii) Studying the functioning of the thyroid gland iii) Studying the functioning of the lungs

Since I don't have a list of all of the radio-nuclides you have studied this year, I will simply give you what elements are typically used for this kind of radio-imaging.
Technetium-99m is used in 80% of Gamma emission imagery and is well-known as the isotope of choice to study the kidneys.
Iodine-123 is another gamma emitter with no beta-radiation, so it is less harsh on the thyroid. It is frequently used to study thyroid gland function because of this.
Xenon-133 or Krypton 81m are both frequently used for lung imaging to establish ventilation and functionality. They are both isotopes of noble gases, so they are very non-reactive as well as being very excitable; they respond well to imaging because they fluoresce when certain frequencies are applied to them.