双块式轨枕的混凝土配合比设计应符合《铁路混凝土工程施工质量验收标准》（TB10424
题型：填空题
问题：
双块式轨枕的混凝土配合比设计应符合《铁路混凝土工程施工质量验收标准》（TB10424）的规定，水泥含量不宜少于（）kg/m3，不宜超过（）kg/m3，水灰比应低于0.45。
题型：填空题
阅读理解
My son was a second-grader. He went to school by bus every day. He was the first student on in the
morning , as we were farthest from school, and the last student off in the evening. I was a teacher myself
and it was a comfort to realize the school staff were all working as hard as I was to provide a safe learning environment.
One day I came home from work and waited for my son to get home for a long time. Then I called
the school. " perhaps he's just a bit late," said the secretary. " I will call the driver to see if those children
are home." A few minutes later, I answered the phone to hear that the other students were home. Then I
called his friends' parents, to see if pe
rhaps he had gotten off at their stop to play. The answers were all " No"
By that time, it was dark and I was scared. My home was in the mountain areas. My husband wasn't
at home, so I forced myself to calm down and decided to go out to look for him. I was about to go out
when the telephone rang; it was from the driver. "He's okay." I heard. " He was asleep on the seats in the
dark, under a couple of jackets. Since it's dark, can he spend the night with my family?"
I was relieved and agreed. Since my son had 
a great adventure, the school started giving a copy of
the list to the driver, so he could check off the children's names when they got off the bus. I think highly of
the school for taking the cautionary(警戒的) step ahead; it is a sign of their concern for students, parents, and staff.
1. From Paragraph 1 we learn that ___________
A. the author's son went home by bus every afternoon
B. the author's son came to school earlier than other students
C. the author's home was farther than that of any other student
D. the author was a teacher in her son's primary school
2. At first the secretary thought ___________.
A. the author's son was still at school
B. the author's son was at his friend's home
C. the school bus would arrive in a while
D. there might be something wrong with the school bus.
3. The author's son probably spent the night ___________.
A. in the bus
B. at his own home
C. at the driver's home
D. in the secretary's office
4. The author wrote the text to ___________
A. praise the school for its quick action.
B. thank the bus driver for his kindness
C. complain about the secretary of the school
D. show her concern for kids safely