a single degree的用法和样例：
- The piecewise cubic Hermite interpolation and cubic spline interpolation were introduced into the analysis of a free beam traversed by a single degree of freedom spring-mass system.
- The letter was written on a single sheet of paper.
- He got over the stream with a single leap.
- The bridge crosses the river in a single span.
- Do you want a single or a return ticket?