Answer:
actual
Step-by-step explanation:
The word "actual" refers to something that exists "in fact" or "in reality." It is similar to the word "real." In this case, we are referring to the land area of Singapore. It seems like the land area of Singapore that actually exists (the land that can be used, as opposed to the land that appears in maps) is not constant, as this is manipulated frequently by developmental pressures.