English » One Word Substitution
Select the option that can be used as a one-word substitute for the given group of words.
A problem that is so difficult that it cannot be answered
Impossible
Solvable
Insoluble
Terrible
option C insoluble is the correct pick for the given set of words.
other options
impossible- that which can not be done
solvable- that which can be solved.
terrible- very; extremely