【答案解析】The biggest hindrance for popularizing LEDs is their initial cost. Households in rural Kenya may spend an average of $7 a month on kerosene for lighting. Although the cost of a solar powered LED lamp over its lifetime is much less than the cumulative cost of fuel, many people cannot afford the initial $25 to $50 outlay for such a lamp. If this problem is solved, LEDs will have very good future.