Answer:
The correct option is A
Step-by-step explanation:
If we take a look at Subject/Verb agreement, pronoun agreements, and modifying phrases, we can see that option A tests OK for all the above tests.
In option B, using the word "they" is a wrong pronoun and does have a referent. Hence this option is also wrong.
Option C and D: The statement clearly states that users are replacing their PCs and hence using the prepositional phrase "beginning" with "for" makes this option invalid.
Option E: It is not personal computer users that are in the beginning of the cycle so this is a logically wrong.