单项选择题 二级公路的路面基层不能选用（）。

单项选择题 听力原文：M: Today, I'm interviewing nine-year-old Carol about her feelings on how people can help save the environment. Good evening, Carol.W: Good evening, I'm glad to be here.M: So, Carol, how can we save the environment?W: By saving water.M: Well, how can we do that?W: By not using too much water when we wash dishes, take a bath, and when we do other things, like watering the plants outside.M: Oh, I think I can do that. What else?W: We should try to make our environment tidy.M: What can we do?W: When drinking or eating something outside, you should keep the garbage until you find a trashcan to put it in because littering makes our planet dirty. Do you like seeing trash all over the ground?M: No, I don't. Do you have any final suggestions?W: Yes. We shouldn't waste paper because trees are being cut down to make the paper. By recycling paper, we save the forests where animals live.M: So, how can children recycle paper, I mean, everyday?W: Well, for example, when I was in kindergarten, I used to save the newspapers so that I could make things out of them, like paper trees, instead of just throwing them away.M: Good idea! What do you do now?W: Now, the children in our neighbourhood collect newspapers once a month to take them to a recycling centre.M: That's great. Well, thanks Carol for your ideas.W: You're welcome.(27)A．The girl's fatherB．The girl's teacher.C．The girl's friend.D．An interviewer.

单项选择题 混凝土拱涵施工，当拱圈中砂浆达到设计强度的（）时，即可拆除拱圈支架。