a reason or a cause? Complete the sentences with " reason" or "cause"

Smoking is one of the.................lung cancer.

Tina gave several .............for her absence. 

What .............. climate change?

Carelessness is often the............ of fires.

What's your ..........for making such a decision?

The .............. of global warming is deforestation and the rise in industrial areas.

What is the................of lightning?

Alcohol is the most common.................of road accidents.

It's our job to establish the.........of the fire

The ...........of his illness is stress” 

The ............ for his success was because of hard work.

The ....... of earthquakes is the heat inside the earth.