∵x＞1，∴x+4x-1=x-1+4x-1+1≥2(x-1)•4x-1+1=5．当且仅当x=3时取等号．
故选B．
当建筑基坑采用排桩、地下连续墙锚杆结构时，锚杆长度设计应符合一定的构造要求，下述（）是正确的。（）
A.锚杆体下料长度应为自由段，锚固段及外露长度之和
B.土层锚杆锚固段长度不宜小于6.0m
C.锚杆自由段长度不宜小于5m
D.自由段长度应超过潜在滑面1.5m
根据下面一段对话内容，从下面选项中选出能填入空白处的最佳选项，其中两项为多余选项。 A: Oh, hi, Tess! I’m sorry. I’m thinking about something. B. （16）A. I am. I have a chance to go onatour. B. A tour What kind of tour A: A music tour. （17）B: Wow! That’ s great. They are pretty famous. A: （18）B: So you’re going to do it A: I don’t know. （19）B: It sure would! Where will the tour go A: （20）B: How long is the tour A: Four months. B: OK, wish you a happy travel! A: Thank you!
该处选项为（）。
A．This tour is the chance of lifetime．
B．It goes all over North America and South America．
C．It looks like you’re dreaming about something．
D．You’ll have to quit school and your job at the store．
E．My agent wants me to go on a tour with Art’s Jazz Band．
F．Have you told anyone about this yet
G．It would be a great opportunity!
