SAT English Practice Question

Although many are familiar with the “Great Wall of China,” the largest structure ever built by humans, the Great Wall of Gorgan, in northern Iran, has also earned the title of "largest man-made structure." This structure, built between the 3rd and 7th centuries AD, served as a protective barrier against the Sasanian Empire. It is said to be the first example of a defensive wall to incorporate a series of defensive towers.

1. A.It is said to be the first example of a defensive wall that incorporates a series of defensive towers.
2. B.It is said to be the first example of a defensive wall, incorporating a series of defensive towers.
3. C.It is said to be the first example of a defensive wall; incorporating a series of defensive towers.
4. D.It is said to be the first example of a defensive wall—incorporating a series of defensive towers.