Question

the euro is the commonly accepted currency for 17 of the 27 member states of the european union. these countries combine to create the eurozone. apart from making traveling easier within european countries, a single currency makes economic and political sense. it reinforces its stability and contributes to low inflation. a single currency is also a logical match to the single market and helps to make it more efficient. using a common currency increases price transparency, eliminates currency exchange costs, and simplifies international trade. lastly, the euro gives citizens a tangible symbol of their european identity.
the student wants to make sure that his word choices are appropriate to inform his audience about the euro. choose the best two words to replace the underlined word.
accompaniment
balance
complement
counter
quantity

Explanation:

• "accompaniment" means something that goes with another thing, but it doesn't convey the idea of a good - fitting relationship as well as "complement".
• "balance" refers to a state of equilibrium and is not relevant to the relationship between the single currency and the single market.
• "complement" means something that completes or makes perfect another thing. A single currency and a single market can be seen as complementary as they work together to enhance economic efficiency.
• "counter" has meanings like opposite or a surface for transactions, which are not appropriate here.
• "quantity" is about amount and not related to the relationship described.

Answer:

complement