当屏幕呈多少角度时，屏幕完全垫在桌子上，屏幕与桌子、后部金属支杆形成稳固的三角形（）
A.35
B.40
C.45
D.90
参考答案：C
The reason why international trade is more costly is that a border typically imposes additional costs such as( )，time costs due to border delays and costs associated with country differences．
A．production
B．tariffs
C．capital
D．goods
简述新药（新生物药物）的研发过程？
