The writer mentions birds and frogs to .
A: provide examples of animal protection
B:show how light pollution affects animals
C:compare the living habits of both species
D:explain why the number of certain species has declined
在我国,当列车自东向西行驶时车轮对哪侧的铁轨磨损较大( )
“a = 1”是“复数a2-1+(a+1)i(a∈R,i为虚数单位)是纯虚数”的( )