天津早期的商业区集中在()、()、()一带。
参考答案:东门外;北门外;三岔河口
—I failed again in the maths exam. How disappointing!
—You it! You never spend time on your maths study.
A.admit
B.stand
C.need
D.deserve
专为升降人员的钢丝绳安全系数小于()时,必须更换。
A.6
B.7
C.10