Question

If lots of people want euros and euros are in short supply, and a few people want japanese yen and yen are in plentiful supply, the yen is likely to _____ against the euro.

Answer 1

in this case the yen is likely to Depreciate against the euro

The value of a currency will increase if it became rare (less owner)
If the amount of yen is abundant but yet it remained unwanted, the value of the yen currency will keep dropping.