Answer:
It is considered to be a bit disrespectful to write to a teacher in an unprofessional, casual manner, the way you would a friend because you aren't close on a personal level. Of course it depends on the teacher and subject of the letter/email/etc. as well.
Answer:
it has two meanings 1.a plant of the Daisy family that has bright rayed flowers typically purple or pink
2.a radiating array of micro tubes associated with centrosome in a dividing cell
As you know, water evaporates in heat, and tropical places are usually very hot! Tropical implies "ocean" so, when an ocean evaporates it leaves a sandy ocean floor, which is a desert, but there are lake sized "puddles" of salt water left over, which is why there is a big salt water lake in the middle of Utah.