A because a controlled experiment only tests one variable.
Answer:
The correct option is;
Glaciers that once covered South Africa have melted and can no longer form.
Explanation:
The Karoo Supergroup that formed hundres of millions of year ago covered the most part of South Africa. The Tillite debris from melting glaciers, in Dwyka Tillite are located at the bottom layers of the Karoo Supergroup, which is an indication that millions of years ago, South Africa was under extensive glacier coverage formed during the movement of the continent past the South Pole
The eventual arrival of the continent to temperate regions away from the South Pole resulted in the melting of the glaciers from which a huge swamp was formed.
