I'll vote for E.
A, B and C are out for using "that" which is modifying "overtime". Its not overtime which causes errors. Its basically the practice of "working an excessive amount of overtime" which is causing errors.
Out of D and E, E is precise and clear. In D "for causing" sounds awkward.
Hmm... you're right
dammit, I know this rule, but it slipped anyway
Las cualidades del agua...porque el agua no olvida que su destino es el mar, y que tarde o temprano deberá llegar a él.