当1 g氨气完全分解为氮气、氢气时，吸收2.72 kJ的热量，则下列热化学方程式正确的是(　　)
①N₂(g)＋3H₂(g)===2NH₃(g)　ΔH＝－92.4 kJ/mol
②N₂(g)＋3H₂(g)===2NH₃(g)　ΔH＝－46.2 kJ/mol
③NH₃(g)===N₂(g)＋H₂(g)　ΔH＝＋46.2 kJ/mol
④2NH₃(g)===N₂(g)＋3H₂(g)　ΔH＝－92.4 kJ/mol

妇女节快乐！

阅读下列短文，从A、B、C三个选项中选出一个能正确填入相应空格内的最佳答案。

    Mr. White wanted to spend a day at the beach. He 1 his daughter Nancy and her two friends, Helen and Karina. They all went to Ocean Beach in New Zealand.

    The group swam and surfed. Then they saw something 2. "They are large fins (鱼鳍)," said Mr. White.

    The 3 saw seven dolphins moving towards them. The dolphins were worried. They 4 the water with theft mils(尾巴). They kept moving around the swimmers. Then one large dolphin swam towards Mr. White and Helen. Next, it dived down underwater. Mr. White saw something grey moving in the 5.

    A shark 6 underwater. It wasn't far from the people. Now the shark was not slow. It moved 7! So the dolphins used their 8 to swim even faster. Each one splashed (飞溅) its tail even more. Then Mr. White knew the dolphins didn't want to 9 him and the girls. These sea mammals (哺乳动物) wanted to keep them safe.

    The dolphins stayed close to the group until the shark 10. When Mr. White and the kids were safe, the dolphins swam away. "You want to say thank you and shake their flippers." Mr. White said. "These dolphins are heroes."

过去，山区公路多为“之”字型盘山公路。现在，兴建高速公路则是逢山开道，遇沟建桥，尽量取最短距离。据此完成下列各题。

栽培于土壤中的农作物，能吸收土壤中的氮、磷、钾等营养物质，而又能抑制有害物质进入植物体，主要是由于（  ）