The reading strategy that would be most helpful in comprehending the sentence is: breaking it up into shorter sentences and phrases.
Reading strategies are the measures that are put in place to aid the understanding of complex texts.
In the excerpt provided, we find that there is a lot of parallelism that made the sentences bulky.
To aid the reader's understanding of the passage, the long sentences will have to be broken down and made shorter.
The passage:
Because most cities would no longer exist, messages would have to be broken up into pieces, scattered throughout the system, moved around cities that no longer existed, and then reassembled at the destination. ARPA combined these ideas with an existing system to create what is now called e-mail.
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