Which of the following statements about the physical geography of north america is true?
a. the largest tributary of the mississippi is the arkansas river.
b. the ancient rock of the canadian shield covers about one-fourth of canada.
c. the most geologically active region of north america is found along the west coast.
d. the mississippi drainage basin is the fifth largest in the world

The correct answer is - c. The most geologically active region of North America is found along the West Coast.

The West Coast of North America is by far the geologically most active region in this continent. This region is part of the so called ''Ring of Fire''. Here we have the boundaries of North American tectonic plate and the Pacific tectonic plate. Because of the processes that are taking place between the tectonic plates there's a very big rift valley that is expanding more and more. The earthquakes are a common occurrence, and the biggest volcano in the world beneath the Yellowstone National Park lies in this part of the continent.

northern hill zone (nhz)

western himalayan regions of j& k (except jammu and kathua distt.); h.p. (except una and paonta valley); uttaranchal (except tarai area); sikkim and hills of west bengal and n.e. states

north western plains zone (nwpz)

punjab, haryana, delhi, rajasthan (except kota and udaipur divisions) and western up (except jhansi division), parts of j& k (jammu and kathua distt.) and parts of hp (una dist. and paonta valley) and uttaranchal (tarai region)