Which describes the sahara?

tropical jungle with a variety of plants and animals

high plains on which many african animals live

a desert that covers the northern third of africa

the terrain between desert and savanna

The correct answer is - a desert that covers the northern third of Africa.

Sahara is the biggest desert in the world. It occupies the northern third of the African continent, thus being the absolutely most dominant landscape feature in North Africa. It stretches from the Atlantic coast on the west, to the Red Sea coastline on the east, and from the plateaus of Central Africa, to near the coastline of the Mediterranean sea. It is a desert that has been a natural barrier for the movement and dispersal of people, animals and plants since its formation, with its vastness, lack of water, lack of food, sand storms, extreme heat.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.