Answer:
c) hypertonic
Step-by-step explanation:
Hypertonic solution - 
It is the solution , having more concentration of the solute than any other solution , is termed to as a hypertonic solution . 
And , similarly , 
The solution with lesser concentration than any other solution , is known as hypotonic solution . 
Hypertonic solution have higher osmotic pressure than another solution , or , in simple words , the solution to be hypertonic in nature , will have more number of solute particles outside the membrane than that is present inside it . 
The most common example of a hypertonic solution , is the salt water solution , 
Hence , from the question , the water in the swimming pool is salty in nature and hence is a hypertonic solution . 
As , the fingers got exposed to this hypertonic solution , and it get shrinked , as the water from the fingers goes to the swimming water , and hence get shrunken and wrinkled .