What need sound to propagate?

If dust particles fall on crops . What happened to the crops?

People who take ores from inside the earth are called

Write an example for poisonous gas which produces from factory?

Solar energy take from which source?

What is the short form of Compressed Natural Gas?

If ozone layer will damage what will happen?

Carbon-monoxide mixes with hemoglobin which in our blood and produces

Why Taj mahal and Qutub minar lost the natural colour?

We can use what type of ovans to prevent air pollution?