Because Astronomers use light-year instead of kilometers to measure distances in the universe because distances in space are so huge that km would be too large to manage.
This could be one of two things, I need a bit more information, but perhaps you can decide.
Drip irrigation otherwise called trickle irrigation delivers water using tubes and emitters to the base of the plant. Subsurface irrigation uses a combination of tubes and emitters and is buried under ground. Good luck
I believe it is A. Teacher because that is a career.
