In in-vitro fertilisation (IVF), several oocytes are taken from a woman receiving treatment. Each oocyte is examined under a microscope. Explain why oocytes with a first polar body are selected for the fertilisation process.
Embryos produced by IVF can be frozen in a solution containing sucrose and various salts, and may later be thawed and implanted. A trial was done to compare the success of freezing oocytes in solution A, the same solution used for freezing embryos, with solution B, a different solution containing different concentrations of sucrose and salts. The oocytes were placed in either solution A or solution B. They were then frozen and kept at $-33^{\circ}\text{C}$. Afterwards, the oocytes were thawed and then fertilised using intracytoplasmic sperm injection (ICSI).
When the oocytes were added to solution A or solution B, they rapidly became smaller. Explain why this happened.
Table 5.1 gives the trial results. Using Table 5.1, explain which solution is the better one to use.
Suggest one advantage of being able to freeze and then thaw oocytes as part of the IVF procedure.