A lake has a big island in the middle. If the island were removed, how would the lake's water level change?

The correct answer is that the lake's water level would stay the same. This is based on the principle of displacement. When an island exists in a lake, it displaces a certain volume of water equivalent to its own volume. If the island were removed, that displaced water does not increase or decrease in overall volume; it simply means there is now a volume of water that fills the space previously occupied by the island. The lake's water level remains unchanged because the volume of water that would have surrounded the island is still present in the lake.

In contrast, the other choices imply changes in water level due to the island removal, either suggesting a rise as the water would flow into the new space or a fall based on other assumptions, neither of which takes into account the principle of displacement adequately. Lastly, the option suggesting that the change depends on the weather introduces variables unrelated to the direct relationship between the island and the water level, which remains stable regardless of atmospheric conditions.