Comprehension Passage
In the following passage, some of the words have been left out. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.
We truly cannot understand the real ______(1)______ of the environment. But we can ______(2)______ some of its importance that can help us understand its importance. It plays a ______(3)______ role in keeping living things healthy in the environment. Likewise, it maintains the _____(4)______ balance on earth. Moreover, the environment gives us countless benefits that we can’t ______(5)______ our entire life.
Which of the following word fits the blank labeled as (4)?
1
pollution
2
economical
3
ecological
4
unnatural