直升机的旋翼恒速，发动机功率改变时：（）.
A.燃气发生器转速改变
B.自由涡轮转速改变
C.燃气发生器转速不变
D.旋翼转速改变
参考答案：A
关于x方程x2-（k+2）x+2k+1=0的两实数根为x1与x2，若x12+x22=11，求实数k的值．
根据句意及首字母提示，写出在本课出现的单词。
1. We each b______ (拿，带) a painting we made in art class.
2. Mine was a picture of the o______.
3. The picture always makes me r______(记住) my holiday.
4. Karen and Jack showed us some p_______.
5. She has long h_______. She combed it ten times.
