A:经世致用的修史观念
B:会通古今的历史视野
C:秉笔直书的勇敢精神
D:高尚的学术道德修养
— “What are you doing?“asked Mom.
— “I am watering flowers,” responded Jack.
现有100g20%的蔗糖溶液,下列说法正确的是( )