弹力纤维的构成单位是()
A．弹力蛋白
B．微原纤维
C．网状原蛋白
D．胶原原纤维
参考答案：A, B
The idea ______ you can own land in a city and do what you like with it is simply ridiculous. [ ]
A. that
B. how
C. whether
D. which
空预器着火报警信号取自何处？
