The conclusion that Asia and Africa had a single landmass is provided by

Answer: (d) All of these

The key treats all three together as the evidence.

The idea

Past land connections are best tested using evidence that is difficult to explain by coincidence. Matching land-organism fossils and continuous rock belts can support a former join. Similar deserts or modern climates can arise separately at similar latitudes and are not enough on their own.

Why the others are wrong

(a) Deserts alone prove nothing.

(b) Climate similarity alone proves nothing.

(c) Matching fossils are the strongest evidence.

The trap

Only fossils are real evidence — but UPSC’s key is (d).

Also know

Fossil evidence is strongest when the organism could not easily cross an ocean and the fossil layers have comparable ages. Mesosaurus across South America and Africa is a standard example; Glossopteris links several Gondwana lands. Geological age, fossil identity and the reconstructed positions should agree. Climate belts can repeat on disconnected continents.