消声器、消声弯管均应设（），其重量不得由两端风管承担。
A、支架
B、单独吊架
C、吊架
D、防晃支架
参考答案：A, C
The cause of the problem is that as we burn ________-coal, oil, and gas-we pump carbon dioxide into
the atmosphere. [ ]
A. fuels
B. articles
C. goods
D. products
Use your head. Nothing taught by others can have the same effect on you as ______learned by yourself．
A．those
B．what
C．that
D．the one
