Sunglasses contain……………to protect our eyes from the sun's rays.

Sodium metal is stored in………………… because it’s very reactive.

Filling a balloon with …………. Makes it moves up in the air.

…………………. is the most dangerous and poisoning gas.

Bulb lamps contain a filament made of ………………

Secret ink is made of

Which is the only metal Liquid at room temperature?

What is the most common element (by mass) forming the planet earth?

Bee sting can be treated with……………

What is the hottest planet in the solar system?

How long does a human red blood cell survive?

How many hearts does an octopus have?

How many bones do sharks have in total?

Optics is the study of what?