In the following passage, some words have been deleted. Read the passage carefully and select the most appropriate option to fill in each blank.

Everything (1) _________ us makes our environment. Living and non-living things form the (2) _________ of our surroundings. Plants, animals and microbes are parts of our environment. Humans have affected the environment in multiple (3) ______ like clearing of forests, building houses and farms, making roads, etc. This is the root (4) _______ of air, water and land pollution on the planet. Ecologists across the globe are making efforts to educate mankind about the (5) _________ of nature, the crisis we face and the methods of managing these crises.

Q:

Select the most appropriate option to fill in blank number 4.

• 1
  motive
• 2
  origin
• 3
  source
• 4
  cause