以下关于数量的增加或减少的表示，正确的是：（）

A、降低到80%，即原来为100，现在为20

B、超额80%，即定额为100，现为180

C、增加到过去的2倍，即过去为1，现在为3

D、减少到过去的2倍，即过去为3，现在为1

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