I am not sure if you can jump to this section But believe me you will
be a winner if you master this. Almost all the tough problems test this.
Now to the question.
Designed to encourage debate
Ask yourself a question what is designed ? it cannot be a place or a person
but some thing a human can create. Logically speaking the next sentence
fragment should convey this right?
B) Designed to encourage debate, some (people ) - hence incorrect
C) Designed to encourage debate, it (something) - this may be ok but what does it
it should alays have an antecedent, which is not present. Also it
is a relative pronoun and cannot be used here
D) Same problem as that of (B)
is an adverb. This has nothing that is modified by Designed to encourage debate