Why Aeroplane windows are round?

What does the following BrainBat signifies?

ABCDEFGHIJKLMNOPQRSTUVWYZ

QQQQQQQQQQQQQQQQQQQQQQQQQ.

Through your logical capabilities, can you make 7 an even?

I know a country, If you remove the last alphabet of its name, it will become a part of your body. Do you name it?

Complete the following series. It.s very logical:

1, 4, 5, 6, 7, 9, 11, __?

What has hands, but can’t clap?

A maths symbol is hidden in the below Bar Graph. Can you decipher it?

I look flat, but I am deep. Hidden realms I shelter. Lives I take, but the food I offer. At times I am beautiful. I can be calm, angry, and turbulent. I have no heart but offer pleasure as well as death. No man can own me, yet I encompass what all men must have. What am I?

Remove two matchsticks to make the below equation correct.

If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?