CAMBRIDGE C1 READING & USE OF ENGLISH PART VI – OPEN CLOZE TEST

TEST 1: BLUE DIAMONDS

Blue diamonds are the world’s most expensive diamonds, with some valued __(at)__ over 350 million US dollars.

However, no one knew ___(until)___ recently precisely where these rare stones came form.

Most diamonds are formed form pure carbon under extreme heat 150 to 200 km underground, and _(it)_ is thought that volcanic eruptions bring them to the earth’s surface.

However, blue diamonds were probably formed somewhere __(between)__ 600 and 800 km down, and in a part of the earth’s interior known __(as)____ the mantle.

Researchers have analysed 46 blue diamonds, all of ___(which)___ contained minerals only found in the lower mantle.

__(Not)___ only were these stones formed four times nearer the earth’s core ___(than)___ normal diamonds, but they also contained an element called boron, __(which)___ is mostly found on the earth’s surface.

What seems to have happened, ___(according)____ to the researchers, is that billions of years ago, rocks containing boron were carried down into the lower mantles by the movements of the earth’s tectonic plates.

TEST 2: BIRDS AS LANGUAGE LEARNERS

Birds gain life skills in various ways. __(although/ though/ while)_____ some of what they know is innate, some is acquired by direct experience.

Scientists in Australia have been exploring a third way: a type of social learning, in ___(which)____ individual birds learn from others ___(rather)____ than through direct experience.

Like many wild animals, birds listen to the alarm calls of other species, ___(making)____ it possible for them to take advantage of many eyes looking out ___(for)____ danger.

The Australian scientists have found that the fairy wren, a small songbird, can learn those unfamiliar calls, ___(without)____ the bird that made the call even being visible.

The researchers trained fairy wrens, ___(in)____ the absence of any predator, by broadcasting unfamiliar sounds together with the alarm calls of other fairy wrens and other bird species.

Initially, the fairy wrens didn’t flee from the unfamiliar sounds. But after training, they usually ___(did)____ so.

The results show the rapid way learning can occur. One researcher says: ‘it’s something that can come in handy, given ___(how)____ hard it can be to see predators and callers in many environments.