Answer: D. Slow start-up.
Answer analysis: First, let's analyze several common advantages of LED lighting and compare the options given.
A. Energy saving: Compared with traditional incandescent and fluorescent lamps, LED lighting has a higher efficiency in converting electrical energy into light energy, so it can significantly save energy during use. This is a significant advantage of LED lighting.
B. Environmental protection: LED lighting does not contain harmful substances such as mercury, and has less impact on the environment during production and use. In addition, due to its high efficiency, it reduces energy consumption and indirectly reduces environmental pollution caused by power generation. Therefore, environmental protection is also an important advantage of LED lighting.
C. Long life: The service life of LED lighting products is usually much longer than that of traditional lighting products, which can reach tens of thousands of hours or even longer. This means less replacement and maintenance costs, which is also a significant advantage of LED lighting.
D. Slow start-up: This option describes a potential disadvantage of LED lighting, not an advantage. In fact, LED lighting has the characteristics of fast start-up and can reach full brightness almost instantly, which is in sharp contrast to the characteristics of traditional lighting products (such as fluorescent lamps) that need to be preheated to achieve stable brightness.
In summary, we can see that options A, B, and C are all advantages of LED lighting, while option D, "slow startup", is not an advantage of LED lighting, but may be its disadvantage compared to some traditional lighting products (although in fact LED lighting starts quickly).
Therefore, option D is not an advantage of LED lighting. Slow startup.