A small island country has a very high population density. It has a shortage of natural resources but has specialized in producing high-end electronics.

d.it must engage in international trade.

Explanation:

If the nation is poor in the supply of natural resources, they will need a steady supply of the natural resources required to produce high-end electronics from other countries where raw material is available.

This means therefore that the country engages in international trade in order to get those raw materials and then after they produce the electronics, they probably sell them to other countries as well. This is the model that Japan adopted.

d. the polar jet stream   lies between the polar easterlies and trade winds should be your answer