Which answer choice shows the correct capitalization for the following sentence?

the sahara desert stretches 3,200 miles across the northern portion of africa.

the sahara desert stretches 3,200 miles across the northern portion of africa.

the sahara desert stretches 3,200 miles across the northern portion of africa.
the sahara desert stretches 3,200 miles across the northern portion of africa.

the sahara desert stretches 3,200 miles across the northern portion of africa.

The correct answer is the fourth option: The Sahara Desert stretches 3,200 miles across the northern portion of Africa.

Explanation:

Since we are looking for the sentence with correct capitalization, we might be tempted to choose the second option. That, however, is not the best choice.

As we know, proper nouns should always be capitalized. A proper noun is a name that identifies a specific place, thing, or person. Thus, the proper nouns in the sentence - Sahara Desert and Africa - should be capitalized since they name a specific desert and a specific continent.

On the other hand, words such as northern, eastern, southern, and western should only be capitalized when they refer to the people who live in a certain region or to their activities. They should not be capitalized when indicating location. That's why the best option is:

The Sahara Desert stretches 3,200 miles across the northern portion of Africa.

b is the answer