I have known that 'it' is well-known as a pronoun missing antecedent, but I am not sure that the using 'it' as a beginning of sentences or clauses can be acceptable or not.
For example:
It can hardly be said that ensuring high production amount would guarantee an economy of scale.
Since the systematic volatility of an economy as a whole cannot be diversified, it is impossible to have an investment portfolio without any risks.
Since dolphins are blue, it is hard to detect them in blue oceans.
Can any of these sentences be acceptable by GMAT. Someone helps me please.
Thanks you
Kawin