1. What is the capital of the Scandinavian nation whose eastern border is the Soviet Union? Helsinki, Finland

2. Which will have dawn first, eastern North America or eastern South America? Eastern South America
3. What is the capital of Idaho? Is it east or west of 100 degrees W longitude? Boise, West of 100 degrees W longitude
4. What country has the longest border on the Arabian Sea? India

Seems like you have all the answers already. Are you just wanting someone to see if they are correct?

Right, again, Reed!

To find the answer to the question "What country has the longest border on the Arabian Sea?" you can follow these steps:

1. Identify the countries that have a coastline along the Arabian Sea. The countries in question are India, Pakistan, Iran, Oman, Yemen, and Somalia.

2. Determine which of these countries has the longest coastline along the Arabian Sea. In this case, the answer is India.

By considering the geographical location and coastline length of each country, we find that India has the longest border on the Arabian Sea.