Why Aeroplane windows are round?

I am a seven-letter word but if you remove four of my letters I will have one left. What word am I?

A man started to town with a fox, a goose, and a sack of corn. He came to a stream which he had to cross in a tiny boat. He could only take one across at a time. He could not leave the fox alone with the goose or the goose alone with the corn. How did he get them all safely over the stream?

Before Mount Everest was discovered, what was the highest mountain in the world?

Can you count the number of triangles in the picture below?

There’s a girl who has a large family. She has an equal amount of brothers and sisters, but each brother only has half as many brothers and sisters. What’s the correct amount of brothers and sisters?

What goes through cities and fields, but never moves?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?

You are trapped in a room with two doors. One leads to certain death and the other leads to freedom. You don't know which is which.
There are two robots guarding the doors. They will let you choose one door but upon doing so you must go through it.
You can, however, ask one robot one question. The problem is one robot always tells the truth, the other always lies and you don't know which is which.
What is the question you ask?

By using 'because' continuously three times, can you make an English statement ?