The correct option is B ushered
Option B is the correct answer because ‘to usher’’ means to take or show somebody where to go, hence according to the statement, cellular phone has shown path/ paved a way for a phase of communication, hence it is the correct answer.
Option A is incorrect because ‘to call’ means to summon, or to call with a particular name, which are both incorrect I’m this context.
Option C is incorrect because ‘delivered’ means to take something (goods, letters, etc.) to the place requested or to the address on it, hence it is incorrect.
Option D is incorrect because ‘started’ means has begun, which is incorrect because ‘cellular phone service has introduced a new phase’ would be correct to use, but ‘started’ cannot be followed by ‘in’, it would be correct otherwise.