Thanks to the Internet, different kinds of information _______ in a short time.
A:can be learned
B:has been learned
C:can learn
D:has learned
已知点P(a,b)在直线y=12x-1上,点Q(﹣a,2b)在直线y=x+1上,则代数式a2﹣4b2﹣1=____
下图所示的四个装置中,设计不合理的是 ( )