The members thought that the task was feasible.

The correct answer is D. workable.

Feasibility is the quality of being able to be done or carried out. Something that is feasible is practical and possible.

Impracticable means not practical or feasible. Something that is impractical is not possible or realistic.

Impossible means not able to be done or exist. Something that is impossible is not feasible or practical.

Difficult means hard to do or accomplish. Something that is difficult is not easy or workable.

In this case, the members thought that the task was feasible, which means that they thought it was possible and practical to do.