In recent days, our general feeling is that we are energetic. At first, we don't know what the reason is. Later, we realized that the oxygen content here is very high. Therefore, compared with Beijing, we absorb much more oxygen. Therefore, we are light-footed, energetic and do not feel tired. One day, according to the schedule, the guide took us to the site of a redwood forest. Just as we approached the Sequoia forest, we felt that the oxygen content began to increase. As if air could be ignited, we all suppressed our voices.