The correct option is D.
The Mexico city was built on the ruins of an old lake. The lake was drained in order to provide the needed land for the city and water has to be regularly pump out of the underground aquifers in order to prevent flooding and also to provide drinking water for the city. This affected the supporting soil structure and result in the sinking of the city. The city has sunk by about 30 feet in the last 100 years and this has caused a lot of damages which are quite expensive to repair.
This is not my area of expertise but as far as I understand we refer to a conditioned sound change if a phoneme when in a certain environment becomes another phoneme - there is a certain condition that propells the change. On the other hand we refer to an unconditioned sound change if all phonemes of, for example, two different kinds are merged into one phoneme - there is no condition as it happens in all instances, and ultimately there is a reduction in the number of phonemes as one is substituted for another.
Answer:
were thinking
Explanation:
when I last saw you, you were thinking of moving to your village
