【正确答案】正确答案： Oceans Almost three quarters of the earth's surface is covered in water. / And around 90% of all the living space on Earth is contained in the oceans. / These vast reserves cradled early life / and continue to be home to a wealth of extraordinary creatures. / At least 230,000 unique species have been documented, / although as humans have only explored a small fraction of the depths, / there may be as many as two million. / As well as being home to marine creatures, / the oceans offer a range of critical services, / including acting as a source of food and regulating the atmosphere. /