Many of the workers currently deployed on the assembly line, hope for the exchanging of their routine jobs for new assignments that are interesting.

for the exchanging of their routine jobs for new assignments that are interesting

for exchanging routine jobs for new assignments that will interest them

to exchange their routine jobs for new assignments that will be new and interesting

to exchange their routine jobs for new and interesting assignments

The grammatical error is exchanging as it uses ing form which does not maintain parallelism in sentences. Therefore options A and B are also eliminated. Option C is because the word new is redundant. Option D is correct and has no grammatical errors.