After Peter had returned from the Sahara desert, he was confined to bed by a ________ disease.
A.mysteriously
B.mystery
C.mysterious
D.mysteriousness

Some sand dunes may be over 200 meters ________ height.
A.on
B.with
C.in
D.at

________ is the process by which a piece of land becomes dry, empty, and unsuitable for growing trees or crops on.
A.deserted
B.desertify
C.desertification
D.desert

The desert biome includes the hottest places in the world because it absorbs more ________ from the sun than land in humid climates do.
A.hotly
B.heating
C.hot
D.heat

Over-exploitation for food, pets, and medicine, pollution, and disease are recognized _______ a serious threat _______ extinction.
A.as / of
B.over / with
C.upon / at
D.to / for

Clearing forests for timber has resulted _______ the loss of biodiversity.
A.in
B.with
C.at
D.for

Life on Earth is disappearing fast and will continue to do so unless urgent action is taken.
A.polluting
B.damaging
C.destroying
D.vanishing

The Bali Tiger was declared extinct in 1937 due to hunting and habitat loss.
A.diversity
B.natural environment
C.reserve
D.generation

World Wide Fund for Nature was formed to do the mission of the preservation of biological diversity, sustainable use of natural resources, and the reduction of pollution and wasteful consumption.
A.extinction
B.development
C.contamination
D.energy

Probability of extinction depends _______ both the population size and fine details of the population demography.
A.from
B.for
C.on
D.in