Concept:The blank needs an idiom that means to admit defeat or give up when facing difficulty.
Explanation:The phrase “throw up the sponge” means to accept defeat or stop trying.
Here, small companies are facing strong competition from big companies.
So, they are likely to give up or surrender in the competition.
“Turn a blind eye” means to ignore something.
“Taste of one’s own medicine” means to receive the same bad treatment one gives to others.
“Take a nosedive” means to fall or decline sharply.
Only “throw up the sponge” correctly shows giving up under pressure.
Answer:Throw up the sponge