Which of the following gases is used in fire extinguishers?

The primary source of energy for most ecosystems is:

The process by which solid turns directly into gas without becoming liquid is called:

Which of the following is used in vaccines to build immunity?

The number of bones in an adult human body is:

The most abundant metal in the Earth's crust is:

Which of the following is an example of a chemical change?

Which of the following waves are used in microwave ovens to heat food?

The device used to convert mechanical energy into electrical energy is:

The deficiency of vitamin B1 causes which disease?

The main gas responsible for global warming is: