—I have a fever.
A:How are you doing?
B:Are you all right?
C:What's the matter with you?
D:Do you have a fever?
要使反射光线和入射光线之间夹角是90°,入射角为( )
函数y=sin(2x+θ)+3cos(2x+θ)为奇函数,且在-π4,0上为减函数的θ值可以是 ()
English is __________ but __________.
某极限运动爱好者协会选定在图中P处开展活动。读局部等高线地形图完成问题。