Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

Until fairly recently, explaining the presence of human beings in Australia was not such a problem. At the beginning of the twentieth century, it was thought that Aborigines had been on the continent for no more than 400 years. As recently as the 1960s, the time-frame was estimated to be perhaps 8,000 years. Then in 1969 a geologist from the Australian National University in Canberra was poking around on the shores of a long-dried lake bed called Mungo in a dry and lonely corner of New South Wales when something caught his eye. It was the skeleton of a woman sticking out slightly from a sandbank. The bones were collected and sent off for carbon dating. When the report came back, it showed that the woman had died 23,000 years ago. Since then, other finds have pushed the date back further. Today the evidence points to an arrival date of at least 45,000 years ago but probably more like 60,000. The first occupants of Australia could not have walked there because at no point in human times has Australia not been an island. They could not have arisen independently because Australia has no apelike creatures from which humans could have descended. The first arrivals could only have come by sea, presumably from Timor or the Indonesian archipelago, and here is where the problems arise. In order to put Homo sapiens in Australia you must accept that at a point in time so remote that it precedes the known rise of behaviourally modern humans, there lived in southern Asia a people so advanced that they were finishing inshore waters from boats of some sort. Never mind that they the archaeological record shows no one else on earth doing this for another 30,000 years. Next, we have to explain what led them to cross at least sixty miles of open sea to reach a land they could hardly have known was there. The scenario that is usually described is of a simple fishing craft probably little more than a floating platform - accidentally carried out to sea probably in one of the sudden storms that are characteristic of this area. This craft then drifted helplessly for some days before washing up on a beach in northern Australia. So far, so good. The question that naturally arises - but is seldom asked - is how you get a new population out of this. If it's a lone fisherman who is carried off to Australia, then clearly he must find his way back to his homeland to report his discovery and persuade enough people to come with him to start a colony. This suggests, of course, the possession of considerable sailing skills. By any measure this is a staggeringly momentous achievement. And how much notice is paid to it? Well, ask yourself the last time when you read anything about it. When was the last time in any context concerning human movements and the rise of civilisations that you saw even a passing mention of the role of aborigines? They are the planet's invisible people. A big part of the problem is that for most of us it is nearly impossible to grasp what an extraordinary span of time we are considering here. Assume for the sake of argument that the Aborigines arrived 60,000 years ago (that is the figure used by Roger Lewin of Havard in Principles of Evolution, a standard text). On that scale, the total period of European occupation of Australia represents about 0.3 percent of the total. In other words, for the first 99.7 per cent of its inhabited history, the Aborigines had Australia to themselves. They have been there an unimaginably long time. (From: First Practice Tests Extra)

More emphasis should be placed on _______ alternative sources such as wind, solar energy, and tides. A. to develop B. develops C. developing D. developed