Question

the most important thing in the world was silence.(change into complex sentence)

Answer 1

The most important thing in the world the thing which was silence .

pls mark me

Answer 2

The answer is ‘There are an important thing in the word, which is silence.’

It is modified into a complex sentence by adding a subordinate clause in it.  

Originally the sentence was a simple sentence and it has been changed into the complex sentence without changing the meaning of the sentence.

Here the noun clause has been added to turn the sentence into a complex one.