Which option fits best in the following sentence?
As the sun ..... slowly in the west, one by one lights went on in the houses.
- dropped
- descended
- sank
- got down
For me 1,2 and 3 works and Ngram also shows up these options.
To get down means to duck or cower, typically quickly and suddenly, as though you are hiding from something or fearing someone shooting you. So this is inappropriate to describe the slow moving of the sunset most of the time, especially when you say "slowly" in the sentence.
When something drops, it falls uncontrollably until it hits the ground. Unless you drop something in water, it's going to fall quickly. So this is also likely inappropriate.
This leaves descended and sank, which both can be used. The word sink can possibly bring up connotations of sadness, e.g. similar to the well-known phrase sinking heart, but descended literally means just to move downward. So either one of these can work depending on the mood you want to convey.