I have a question about why a parenthesis is necessary in a sentence instead of a relative clause: Why it should be:
Such an impact, many scientists believe, would have blocked the planet with debris.
Instead of:
Such an impact many scientists believe would have blocked the planet with debris.
I think I can understand the second one as "Many scientists believe such an impact would have blocked the planet with debris.
byw, it is a question from ACT English.