The correct answer is C) Mongolia has not a seaport, which makes it difficult to transport goods.
It's harder for Mongolia to export goods than it is for China and Taiwan in that Mongolia has not a seaport, which makes it difficult to transport goods.
Seaports represent a great advantage to countries that have shores. Cargo ships can transport the goods to other countries so much easier that countries that do not have seaports. That is the case of Mongolia. Compared to China and Taiwan, these countries have seaports and cargo ships that facilitate the transportation of products worldwide. That is one of the reason is a commercial superpower and part of the reasons why the United States is having a trade war with China in this very moment.
The other options of the question were a) Mongolia has a command economy and few goods to export, b) Mongolia charges higher export taxes than China and Taiwan, and d) Mongolia produces goods of lower quality than China and Taiwan.