What is always in front of you but can’t be seen?

Why is it against the law for a man living in Delhi to be buried in Mumbai?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth, I am dissolved into air. What am I?

I look at you, you look at me, I raise my right, you raise your left. What am I?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

Can anyone tell me a word in the English dictionary which has a silent 'z'?

Railroad Crossing, look out for the cars. Can you spell that, without any R's ?

Which five letter word can be added at the end of below word to form a
valid word?

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What has 88 keys?

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?