Read the following passage and mark the letter A, B, Cor D to indicate the correct answer to each of the questions from 21 to 25.

Kandimalal is a large crater in the Kimberley region of Western Australia, 145 kilometres from the town of Halls Creek. Scientists say that Kandimalal was formed about 300,000 years ago when a meteorite struck the earth.

Measuring some 880 metres across and about 60 metres deep, Kandimalal is the second largest meteorite crater in the world. The crater used to be 150 metres deeper, but it has since been filled with wind-blown sand from the Great Sandy Desert. Although the area is arid, rainfall collects in the centre of the crater, and this allows trees to grow there.

Kandimalal has long been a part of the dreaming of the local Djaru people. One of the stories says that a rainbow serpent slithered through the earth and came to the surface in the centre of the crater.

The first time Kandimalal was seen from above was in 1947 during an aerial survey of the region. The area around the crater became a national park in 1969 and has since become popular with tourists who have four-wheel drive vehicles.

Scientists believe that Kandimalal was formed by ________.