When and where were playing cards invented?

When was the ship’s distress signal SOS/Save Our Souls used first?

What is the process of food irradiation? And how does it prevent food spoilage?

How do we know that there is a massive black hole at the centre of our Milky Way galaxy?

Who invented the first personal computer?

What is pig iron? How did this name get derived?

How was the circulation of the blood proved?

Why can’t we see in the dark like cats and owls?

What is the raw material of menthol which is used in a wide variety of products such as pain balm, toothpaste, cough syrup and peppermint etc.

Which is the remotest inhabited island? How far is it from the nearest human habitation?