铁路货车篷布不足时，经铁路局批准，货车篷布与货主自备篷布可以混苫。
参考答案：错
螺杆挤出过程中匀化计量段中物料总体积流量如下式所示，试简述式中各项物理意义。
Which of the following statements is true of futures contracts()
A. All futures contracts are bought and sold on organized exchanges and the terms of futures contracts are determined by the buyers and sellers themselves.
B. The Clearinghouse serves to guarantee the performance of all parties to futures contracts.
C. Both are true.
