已知线段AC和BC在同一直线上，如果AC=10cm，BC=6cm，D为AC的中点，E为BC的中点，则DE=( )
2cm或8cm
下列物质中，主要成分是由 天然有机高分子组成的是（ ）
A．红糖
B．瘦肉
C．塑料
D．武德合金
The doctor asked the man what _____. [ ]
A. the matter was
B. was the wrong
C. was the matter
D. was his trouble
