Leading up to the dot com crash, company mergers, lawsuits, and accounting scandals raised fears that internet companies would be unable to maintain their market share.
Sentence structure is -> Leading to an dot com crash event, mergers, lawsuits and scandals raised fears..what sort of fears? that internet companies would be unable to maintain their market share.
A. that internet companies would be unable to maintain
this is concise and correctly describes the fears. 'would' correctly identifies uncertain event in the future
B. that there would be internet companies unable to maintain
there would be -> is wordy
C. of internet companies unable to maintain
raised fears of internet companies - is not correct way to indicate what sort of fears. unable to maintain modifies companies, it is already assumed those companies are unable to maintain the market share.
D. of internet companies that would be unable of maintaining
raised fears of internet companies - is not correct way to indicate what sort of fears. when we describe ability of something or someone, we say ability to do X. companies would be unable to maintain and not of maintaining.
E. of internet companies that are unable to maintain
raised fears of internet companies - is not correct way to indicate what sort of fears. this sentence also indicates/describes fears of those companies that are already unable to maintain the market share.
A is the answer!