Increasing costs, when unmitigated simultaneously by gains in revenue, may lead to a profit reduction that would damage a company in the long term.
First split is
when vs
if. Either could work.
Second split is
lead vs
leads.
costs is plural, so the plural form of the verb is required (
lead). Go through the rest one-by-one
A) when unmitigated simultaneously by gains in revenue, may lead
Mitigated means "make (something bad) less severe, serious, or painful". Unmitigated means "absolute; unqualified". I don't know what the term for words that seem opposite not actually being opposite - false friend?
B) when not mitigated by a simultaneous gain in revenue, potentially leads
Wrong for
leadsC) when they were unmitigated by simultaneous revenue gains, may lead
As with A.
D) if not mitigated by simultaneous revenue gains, potentially leads
wrong for
leadsE) if not mitigated by simultaneous gains in revenue, may lead
Only option left!
if-clause works well
not mitigated is the opposite of mitigated
costs...lead is good
E