双轨运输巷采区装载点，两列列车最突出部分之间的距离，对开时不得小于（）。
A.0.5m
B.0.7m
C.0.8m
参考答案：B
绝对值为4的实数是（ ）
A．±4
B．4
C．-4
D．2
Open Shortest Path First(OSPF)is a (71) routing algorithm that (72) workdone on the OSI IS-IS intradomain routing protocol．This routing，as compared todistance—vector routing，requires (73) processing power．The Dijkstra algorithm is usedto calculate (74) OSPF routing table updates only take place when necessary， (75) atregular intervals．
A．routes B．road C．distance D．cost
