阅读理解
Alisa was walking around the swimming pool. Her friend Maria was waiting for her. "Come on, Alisa!" Maria said. "Let's jump off the diving board (跳水版)."
"No way! I can never go that high," said Alisa.
"Don't be scared," Maria said. "It's really fun."
Alisa walked away and sat on a bench.
"You go. I'll watch you," said Alisa.
"You don't know what you're missing," said Maria. Then she climbed up the tall ladder (梯子). It made Alisa scared just thinking of being up there.
Maria jumped off the board and then climbed out of the pool. She walled to Alisa. "Come on, Alisa; just try it. It's wonderful!" she said.
Alisa looked up at the board. Maybe it was time to try something new. OK, she said. Alisa climbed up the ladder for the diving board. The water looked far, far away. She wanted to turn back to climb down the ladder， but that would be too embarrassing. There was only one thing to do.
Alisa walked to the edge (边缘) of the board. Then she closed (闭上) her eyes and jumped. She got into the water in no time. "Wow, so wonderful! I like it!" she shouted.
2NH3(g)，673K、30MPa下，n(NH3)和n(H2)随时间的变化关系如下图所示，下列说法正确的是 