You ______a teacher. I ______ a student. My sister ______a student, too.
A:am; is; are
B:is; are; am
C:are; am; is
D:are; is; is
有关青春期生理和心理健康,不正确的是( )
河宽420m,船在静水中速度为4m/s,水流速度是3m/s,则船过河的时间可能是( )
要使反射光线垂直于入射光线,入射角的大小为____;沙漠上空出现海市蜃楼是属于光的____(选填“反射”或“折射”)现象。