题目

玉米叶肉细胞中有一种酶，可通过一系列反应将CO2“泵”入维管束鞘细胞，使维管束鞘细胞积累较高浓度的CO2，保证卡尔文循环顺利进行，这种酶被形象地称为“CO2泵”。图1表示玉米CO2同化途径，图2表示进行自然种植的大棚和人工一次性施加CO2后的大棚内玉米光合速率变化曲线。回答下列相关问题：（1）卡尔文循环离不开光照，理由是_______________。当环境中光照增强，温度过高时，玉米光合作用速率不会明显下降甚至可能会提高，其原因是____________Kindness is not always a straight line. I was traveling in a city of Central America with a friend, and we were looking for a post office. we were standing on a street corner and did not know what the Spanish word for “post office” was. One kind man could see we were in difficulty and came up to us. We tried to explain what we were looking for, and he said, “Oh, yes, yes.” He led us down all these little streets. It seemed like we walked for miles. Finally, he pointed us to a building without any name on it. But when we went in, we found it was not a post office.When we walked out and were again standing around looking lost, a woman soon came up and asked if we needed help. Again we tried to explained where we were going. The woman said she could help us. Then we followed her to another building which also had no name and we found it was not a post office, either. At this point we decided not to listen to anybody else.But then another person came up and said, “I can help you.” We said, “No, thank you.”But he didn't listen to us. He actually caught me by the hand and pulled me through the streets. Circling around, we came back to the first corner we had been standing on when we began. He pointed across the street, and there was the post office.1.How many people helped the writer and his friends look for a post office in the story?A. Two. B. Three. C. Four. D. Five.2.How did the first kind man help them?A. He helped them find the post office. B. He led them down all the little streets.C. He forced them to walk for miles alone. D. He taught them to speak Spanish.3.The woman led them to another wrong place because ________.A. she wanted to fool them B. she wanted to sell thingsC. she didn’t know the way D. she wanted to play a joke4.What does the writer want to tell us?A. Kindness is not always a straight line.B. Don’t listen to anybody else easily.C. We must learn its language of a foreign country.D. It’s important to stand where we are at first.