阅读理解。 A Low-Carbon Economy (LCE) or Low-Fossil-Fuel Economy (LFFE) is an economy which has a smallest output of greenhouse gas (GHG) release into the atmosphere, but specifically refers to the greenhouse gas CO2. Recently, most of scientific and public opinion has come to the conclusion that there is such an accumulation of GHG (especially CO2) in the atmosphere due to human-related activities that the climate is changing. The over-concentration of these gases is producing global warming that affects long-term climate, with negative impacts on humanity in the foreseeable future. Globally performed LCEs therefore, are proposed as a means to avoid catastrophic climate change, and as a forerunner to the more advanced, zero-carbon society and renewable-energy economy. Some nations are low-carbon societies which are not heavily industrialized or populated. In order to avoid climate change at any point in the future, all nations considered carbon-thick societies and societies which are heavily populated, should become zero-carbon societies and economies. Several of these countries have promised to become 'low carbon' but not entirely zero carbon, and claim that release will be cut by 100% by offsetting  release rather than stopping all release. In other words, some release will continue which will be offset, so they are not low-release. Nations seek to become low-carbon economies as part of a national global warming reduction strategy. A comprehensive strategy to manage global warming  is carbon neutrality , geoengineering and adaptation to global warming . Nuclear power, or, the proposed strategies of carbon collection and storage (CCS) have been proposed as the primary means to achieve a LCE while continuing to exploit non-renewable resources; there is concern, however, with the matter of spent-nuclear-fuel storage, security and the uncertainty of costs and time needed to successfully carry out CCS worldwide and with guarantees that the stored release will notleak into the atmosphere. Alternatively, many have proposed  renewable energy should be the main basis of a LCE, but, they have their associated problems of high-cost and inefficiency; this is changing, however, since investment and production have been growing significantly in recent times. Furthermore, regardless of the effect to the atmosphere by GHG releases, the growing issue of peak oil may also be reason enough for a change to a LCE. 1. Low-carbon economy is encouraged for the following reasons except that ______. A. too much greenhouse gas CO2 is released B. the over-concentration of greenhouse gases is producing global warming C. it can avoid catastrophic climate change D. low carbon and zero carbon nations and societies claim for it 2. The underlined word in the first paragraph probably means ______. A. warning B. pioneer C. symbol D. guide 3. According to the passage, which of the following is NOT true? A. Nuclear power could act as one of the primary means to achieve a LCE. B. There's worry about spent-nuclear-fuel storage, security and the uncertainty of costs. C. The stored release will be likely to leak into the atmosphere. D. Renewable energy tends to become the only means to achieve a LCE. 4. From the last paragraph, we can infer that the writer's attitude toward the proposal of adapting renewable energy is ______. A. negative B. positive C. self-confident D. doubtful