The correct answer is C. amazing.
The word “marvellous” means “causing great surprise or wonder.” It is often used to describe something that is very impressive or extraordinary. In this case, the speaker is using the word to describe the discoveries of modern science. These discoveries are often groundbreaking and have the potential to change the world. They can be awe-inspiring and thought-provoking.
The other options are not as accurate. The word “praiseworthy” means “deserving of praise.” This is not necessarily the case for all of the discoveries of modern science. Some of them may be controversial or have negative consequences. The word “commendable” means “worthy of praise or commendation.” This is also not always the case for the discoveries of modern science. Some of them may be accidental or have unintended consequences. The word “admirable” means “worthy of admiration.” This is a more general term that could be applied to any of the discoveries of modern science. However, it does not capture the specific sense of wonder and surprise that is evoked by the word “marvellous.”