A:n2n-1
B:n+12
C:n2
D:n-12
烧杯中盛满一定浓度的醋酸溶液(溶液密度约为1 g/cm3),全部倾倒后烧杯内仍残留0.5 mL溶液,用每次20 mL蒸馏水冲洗了2次,此时烧杯中残留的醋酸溶液的浓度约为原先的( )
根据图片信息,找出相应的句子。
① ____ A. I listen to the radio.
② ____ B. I play on the computer.
③ ____ C. My mother, my father and I eat supper.
④ ____ D. I talk on the phone with my friend.
⑤ ____ E. I watch TV.
已知Rt△ABC中,∠C=90°,BC=3,AB=5,那么sinB的值是( )